Aquarium Nitrogen Cycle & Cycling A Fish Tank




Aquarium nitrogen cycle & cycling a fish tank

Sharing is caring!

Immediately after setting up your aquarium, it can be very tempting to head to the pet store and buy a bunch of fish. Unfortunately, you’ll often find your new aquarium inhabitants upside down within a week if you do this.

It can be very demotivating to find your new tank full of dead fish, but fortunately, these unnecessary deaths can easily be prevented by properly cycling your fish tank.

Keep reading to find out everything you need to know about the nitrogen cycle, cycling your aquarium, and how you know your tank is ready for fish!


All new aquariums go through a stage where they are a toxic and extremely dangerous closed environment for any live animal.

Aquariums are in this toxic stage for about one to two months after being set up. There are little to no populations of beneficial types of bacteria to convert toxic compounds from ammonia to nitrite to nitrate during this time.

As we’ll discuss, toxic ammonia and nitrite are directly harmful to fish and invertebrates and unsustainable for most aquatic life. Even nitrate, usually non-toxic to freshwater fish, can become dangerous at higher toxic levels.

To prevent fish from suffering through high ammonia and nitrite levels, hobbyists need to let their aquariums cycle and let bacterial colonies form on their own to keep the water safe.

To understand when your aquarium is ready to add a load of fish and what you should do if you’ve already introduced them, it’s essential to know the nitrogen cycle first.

How to cycle your aquarium | Step by step guide!
Hover over image to pin to Pinterest

The nitrogen cycle

The nitrogen cycle is necessary for the success of both freshwater and saltwater aquariums. This process converts the nitrogenous compounds in ammonia into nitrite and then into nitrate.

In the aquarium keeping hobby, the phrase “nitrogen cycle” usually describes the first 4-6 weeks of a tank’s life when water parameters are settling.

In actuality, the nitrogen cycle is always happening in the aquarium environment and facilitates safe water parameters for fish, invertebrates, and plants. The actual cycling of an aquarium system refers to when the necessary bacteria population is established in the beginning stages.

The nitrogen cycle can be described in two main steps: nitrification and denitrification.


The nitrogen cycle and the growth of beneficial bacteria are triggered by the presence of ammonia (NH3) and ammonium (NH4). This occurs naturally as fish live, eat, expel harmful waste, and die, but sometimes it requires human intervention to get started.

You can also introduce an ammonia source into the aquarium water through fish waste product, leftover food, dead plants, and other organic matter breaking down. Ammonia cannot be avoided and needs to be processed by a special nitrogen-fixing bacteria called Nitrosomonas

Chemically, these bacteria convert ammonia (NH3) and ammonium (NH4) into nitrite (NO2).

Ammonia is very toxic to all aquarium inhabitants and will cause gills and internal organs to burn. Thus, You should always keep the detectable levels of ammonia at 0 ppm if any fish are present in the tank. 

Once ammonia has been introduced and begins to increase, Nitrosomonas populations will also increase. You can observe this in the rise and fall of aquarium ammonia levels as bacteria start their natural process.


Thanks to Nitrosomonas, denitrification will begin once nitrite is present in the water column.

Denitrification is the conversion of nitrite (NO2) to nitrate (NO3) by another type of bacteria, Nitrobacter.

This process will start shortly after ammonia levels rise but can take longer in a larger-sized aquarium. During this time, the ammonia and nitrite levels will decrease, with ammonia beginning to read at 0 ppm consistently and nitrite slowly waning. 

It can be tempting to add aquarium fish during this time, but an influx of additional amounts of ammonia can cause another cycle process to start as the population of bacteria is not fully established yet. Also, remember that nitrite can be just as harmful as ammonia to healthy fish and invertebrates.

Once nitrite reaches 0 ppm, and only nitrates are observable in the system, the tank is considered cycled.

Nitrification and denitrifcation in the aquarium

From start to finish, an aquarium cycle will look like this:

  • Ammonia and ammonium enter the healthy aquarium and cause Nitrosomonas to start converting them into nitrite.
  • As bacteria colonize the aquarium and become your biological filter, you will notice levels of nitrites rise. At the same time, ammonia will start to decrease slowly.
  • Nitrites will be converted to much less toxic nitrates by the second colony of Nitrobacter bacteria. Eventually, both ammonia and nitrite will read 0 ppm, and only nitrates will be present. The tank is then considered cycled.

Nitrates will stay in the aquarium unless a partial water change is performed; it is recommended to exchange 75%-100% of the water after a cycle has been completed to reduce the nitrate reading below 20-30 ppm and get the tank going in the right direction.

This will not undo the cycling process as the bacteria live on surfaces and not in the water column; however, sometimes bacteria become free-swimming which can be seen in cloudy tanks experiencing a bacteria bloom.

At this point, you may safely introduce fish and invertebrates into the aquarium. Make sure to add livestock slowly to prevent a mini cycle from happening again.

Plants in the aquarium

Though fish and invertebrates can’t be present during a tank cycle, aquarium plants actually can. In fact, underwater plant life can help lower ammonia and nitrite levels so much that you might get something known as a ‘silent cycle.’

Plants use ammonia, ammonium, nitrite, and nitrate to grow. If you add enough plants during the cycling process, they may use nutrients so fast that you do not get to see your ammonia or nitrite levels rise or fall dramatically.

This can be pretty confusing to see, and you might wonder why your tank isn’t cycling. You will still need to trace the conversion of ammonia to nitrate with an ammonia test kit to guarantee the tank is fully cycled.

This method can be tricky because it’s nearly invisible and extreme and swinging parameters can hurt plants. For the most part, average aquarium plants will be able to withstand higher nutrient levels, but more sensitive ones might melt away.

Some expert hobbyists have been able to cycle a densely planted aquarium with hardy fish species this way, though it’s not the recommended method for most.

How to cycle an aquarium

There are several ways to cycle an aquarium; most involve introducing ammonia into the tank to trigger the growth of bacteria colonies.

You will need an aquarium test kit, either for a saltwater or freshwater fish tank, depending on your setup, to successfully cycle an aquarium. While local aquarium stores may offer free testing, they usually use paper strips, which are wildly inaccurate.

You will need liquid testers for pH, ammonia, nitrite, and nitrate levels for the best results. This way, you will see the levels rise and fall across the following weeks.

A liquid tester like the API Freshwater Master Test Kit is much more accurate than test strips and cheaper in the long run as it can last you many years. 

Cycling with fish

This traditional method is the oldest and most common way to cycle an aquarium is to cycle with fish. This means putting some cheap fish into the tank, so ammonia is introduced and starts the cycle.

Pet stores often recommend this method because it means extra profit for them when fish die. But, cycling an aquarium this way actually takes longer, requires regular water changes to keep the fish healthy and alive, and usually permanently damages or kills the fish involved.

In no way, shape or form is this method recommended, though more advanced hobbyists can sometimes keep up with the water changes needed, especially if the tank is densely planted.

Luckily, there are plenty of cruelty-free options and easier alternatives to cycle an aquarium.

Cycling with food

As mentioned earlier, uneaten food is broken down into ammonia, which is needed to start an aquarium cycle.

A large, uncooked shrimp or fish food can be added to the tank and left to decay until the tank is well into the cycle.

This fishless method is not entirely risk-free because rotting, uneaten fish food often attracts unwanted bacteria and dirties the tank water. The smell can also become obnoxious after a few days.

Because of this, a significant (90-100%) water change should always be done before introducing fish to a tank cycled this way.

Though not the cleanest method of cycling an aquarium, cycling with food is one of the most tried and true methods. Just make sure that there is always a constant source of ammonia being introduced into the system so that bacteria continue growing.

Cycling with ammonia

Pure household ammonia is sold in garden stores and some supermarkets as a cleaning product. This is one of the cleanest and most accurate ways to cycle an aquarium.

Ammonia is also sold in smaller containers by several brands such as this one, specifically for aquarium use. Add about five drops of ammonia per ten gallons of water. 

There are different dosing methods, but ideally, the preferred method is to add just enough ammonia so that the bacteria continue growing. It is possible to overdose ammonia, which can stall a cycle.

Once you start to see nitrates appear, it’s time to stop dosing. Allow ammonia to hit 0 ppm and perform a significant water change.

At this point, you may add fish. However, if you plan on delaying adding livestock for any reason, you will need to continue dosing the tank with ammonia to keep the bacteria from starving.

Seeding the filter

Using cycled filter media that already has the correct beneficial bacteria colonies from another tank can quick-start the nitrification process in your aquarium.

This way, you can add fish instantly, but you do run the risk of introducing diseases or pests from the ‘donor’ tank into the new one and starting a mini cycle. This method is very popular due to its near-instant results.

If you don’t own a cycled aquarium, you can ask friends who own an established tank or pet or aquarium stores. They might be able to supply you with some seeding material, though this dramatically increases the risk of introducing harmful bacteria and parasites.

Use the media as soon as possible. It should be transported in water from the tank it was in and should never sit for more than one hour before being put in the new tank’s primary filtration.

If the filter media is exposed to oxygen for too long or left in stagnant water, the beneficial bacteria will start to die and begin another cycle.

If you need to let the used media sit for a longer time for whatever reason, put an air stone into the bucket to provide the beneficial bacteria with oxygen and flowing water to prevent them from dying.

Bottled bacteria

The next best option for quickly cycling a tank would be to use bottled bacteria. In essence, the necessary bacteria needed to cycle an aquarium can be purchased in bottle form from your local fish or pet store.

It is recommended to always check the expiration date on these products as they can usually only be stored for about a year and keep them in a cool, dark place like the fridge (not the freezer!).

However, don’t assume you can add fish right away: these products are best used as a ‘kickstart’ for your cycle, so the nitrogen cycle process doesn’t take as long. They do work, though, especially when combined with a high-quality water conditioner like Seachem Prime to remove traces of ammonia and nitrite.

Simply follow the instructions on the label, and you will have a greatly accelerated healthy nitrogen cycle for your aquarium!


Cycling your aquarium before adding any fish is one of the most important steps to achieving a healthy little ecosystem, and it’s one you should never skip.

The ammonia and nitrite spikes that result from failing to cycle an aquarium properly can cause fish death and weeks or months of trouble, constant water changes, having to buy expensive products, and can completely ruin the aquarium hobby for you.

If you have any more questions about cycling an aquarium or something to add to this article, be sure to leave a comment below!

Sharing is caring!

82 thoughts on “Aquarium Nitrogen Cycle & Cycling A Fish Tank”

  1. Hello. This is a very informative article, thank you for that. I was wondering if I should start cycling my tank with live plants or without them as I think the ammonia levels (I’m using fishless cycling) could harm the plants.

    • Hello Belle!
      Plants are actually very helpful for the nitrogen cycle. Plants mostly use nitrate, but they can also take up nitrite and ammonia/ammonium, which can help speed up the cycle and/or lower the levels of nutrients in your system during the cycle. This is a good and bad thing and you can sometimes get a ‘ghost cycle’ where the plants are so efficient that you can’t even tell that the tank is cycling.
      But long story short, plants are good for your nitrogen cycle and can be added at any time!

  2. Hi I have almost finished cycling my 230 liter tank. I already have 7 fish in their current tank. 4 white cloud mountain minnows and 3 peppered Cory. When the tank is cycled and I can put my fish in, will I be able to out them all in at the same time?.

    I am planning on putting their existing filter in their new tank and running them alongside each other for a while. I’m worried about separating the fish from each other but at the same time don’t want to overload the

    Any advice would be greatly received.

    • Hi Julia!

      230 L is a pretty big tank! That is also a good idea for the filter, just so some beneficial bacteria is already established; some hobbyists just move the media from one filter to the other, but if you can afford to run both at the same time, I don’t see how it could have a negative impact in any way.
      I would have no worries about putting your minnows and cories in all at once; however, I would try to get more fish as soon as you can. Both of those species need to be kept in groups of at least 6 or more and might have difficulty finding each other in such a large tank. Maybe you can transfer the fish you have already into the new tank and use the old tank as a quarantine/hospital tank for the new additions.
      What else are you planning on getting?

      • Hi Jennifer,

        Thank you for your quick reply.

        That is great you don’t see any problems in putting them all in at the same time. That’s one thing I was worried about, separating them (even if it was for only a few days).

        I thought it would be a good idea to run the existing filter along with the new filter but thought I would check, and ask somebody with more knowledge.. How long do you think I should leave it in the new tank?.

        The tank has been cycling for just over 3 weeks and 3 days (not quite cycled yet but almost there) with a part of the sponge from the existing filter put into the new filter, Some existing gravel as well as a new bag of gravel, some moss balls from their existing tank (with the rest to be added when I move them) As well as existing ornaments and some existing plastic plants. I have been feeding the tank with flake food. I also have a air stone running.

        Yes I definitely would like to get some more fish when the other fish have settled into their new home and everything is stable. I agree they could easily get lost in there, they are only tiny.

        How many maximum do you think I could eventually have in that sized tank.?. I would like to keep to what I know and get some more peppered Cory and white cloud mountain minnows.

        I am going to keep their existing tank as a quarantine/emergency tank. It’s good to have a spare in these events, I agree.

        Thank you for your advise. That has put my mind at ease.


        • I would probably keep the filter running maybe for a month if you’re able to; the first 3 months of a new tank tend to be the hardest and extra established bacteria definitely won’t be a bad thing to have, so long as your keep up with the maintenance as you normally would.

          While you have a big tank, it’s important to consider that the two species, white cloud minnows and cories, tend to do best in lower water temperatures (low 70s, 22ยฐ C). But for the most part, you should be fine getting tetras, cherry barbs, gouramis, etc. The trick will be finding the best water temperature to accommodate all of them, but as long as you stay with community fish, you should have no problems otherwise. Also, don’t be afraid to get larger schools for your tank; I tend to prefer a larger school than a large diversity of fish!

          • Hi Jennifer,

            That will be no problem for me keeping the old filter running alongside the new filter for a month or more if I need to. Yes their water is about 22 degrees as it happens, so perfect.

            I think I will probably stick with the minnows and cories. Although the other fish are lovely, like you say yourself I would also prefer to keep to larger schools of the same species.

            I have actually just moved them over to their new tank today. All the levels were perfect and after cleaning the gravel, replacing a lot of the water, and moving the old filter over and putting it on straight away, I tested the levels again just to be sure and they were all perfect. I also tested the 2 different tanks pH levels and temperatures before putting them in.

            They all seem happy, the minnows are playing and the cories are doing their usual cleaning. It is strange seeing them in such a big tank and like you said before they seem lost. Although the minnows are sticking together and the cories are doing a great job and picking up where they left off, I am looking forward to adding to their school and introducing some new friends for them.

            Obviously I know I need to keep a close eye on things and will be testing the water daily to check things are staying as they should. Fingers crossed things go to plan. I may even test the water again later today.

            How long do you think I should leave it until I add more fish to their school?. As long as levels stay safe of course.

            Thank you again for taking the time to reply to me. It is very much appreciated.

            Julia (from the UK).

          • Really great job on the transfer! It seems like everything went smoothly and you did everything as near perfect as you could. As for when to add new fish, your tank will kind of tell you that. I downgraded from a 60 gallon (227.1 L) saltwater tank to a 10 gallon (37.9 L) tank in one go and probably waited 2-3 weeks to add a new fish. At the very least, I would probably give it a week to make sure that no mini-cycle started as a result of just kicking stuff up and upsetting parameters. Just keep an eye on your parameters and you should be good to go soon :-)!

          • Hi Jennifer,

            It wouldn’t let me reply to your latest message. So I’ve replied to this message instead.

            Yes things seem to be going really well. I tested the levels yesterday and again today and they were all perfect.

            All the fish seem really happy and active and seem to have settled well into their new home.

            That’s great I will wait a few weeks until adding any new fish. I agree I need to make sure things are stable first. That makes sense. So far so good at the moment.

            Thank you again for all your advice and help it has been very helpful and invaluable.

            Take care.


  3. Hello! I understood all of that and ready to get started! But my question is when to do the water change after adding my fish. and how often should I do it? Don’t want to do the same mistakes I did before lol. Ps: 15 gallon tank with a betta fish and one or two snails, no live plants.

    • Honestly, it’s all up to the tank to decide how often it needs a water change. People have had success with weekly, biweekly, and monthly water changes; some don’t even do water changes at all. I personally have a 10 gallon saltwater tank that I do ~20% water changes on every week.
      Water changes are really meant to help remove nitrates and phosphates and replace trace elements. Since you have a good-sized tank for your betta (good job giving your betta a nice home!) and little bioload otherwise, you probably won’t need to do weekly water changes.
      You could probably comfortably get away with 20-30% water changes every other week to start. If you notice more algae/cloudy water, try boosting it up to every week. If you’re finding that your water is too ‘clean’, then try once a month.
      Remember that a healthy tank should have some nitrates and phosphates!

  4. Hello Mari!
    So I have been cycling my tank for almost 3 weeks now and it is doing fantastic! My nitrite levels are really high and my nitrates are now at almost 30 ppm. I’ve still been dosing my tank with ammonia to give the bacteria nutrition as well. My question is do the ammonia levels drop to zero while you’re still dosing the tank with it or do you stop dosing the tank in order for the ammonia and nitrite levels to drop to zero?
    Thank you! ๐Ÿ™‚

    • Hi Samantha,
      It sounds like your tank is almost ready! Just not quite yet.
      The general rule is that your tank should be able to process ammonia within 24 hours; meaning that ammonia will read 0 ppm within 24 hours of dosing. So keep dosing (or follow the directions on the product you are using) until this happens.
      Once this happens, your tank is considered cycled and it is then recommended to do a big water change, between ~50-75% with some hobbyists even doing 90%+. At the end, you should have 0 ppm ammonia, 0 ppm nitrites, and <10 ppm nitrates.

      • Thanks for the advice! So I do have another question pertaining to the same tank. It’s been a few days and I tested my ammonia, nitrite, and nitrate levels and all of them are at the highest levels that they can be. Should I do a water change or anything else or is that just part of the cycle?

        • Hm… Are you still dosing the ammonia? If so, I would stop and then see if your tank starts to settle down. I don’t think you should be too concerned yet; every cycle is different, and this might just be how your tank is reacting. But if you stop dosing and after a ~week your parameters are still super high and don’t seem to be moving, I would do a water change. When did you start the cycle?

          • I started the cycle nearly two months ago. I gave it about four or five days without dosing and the ammonia levels were almost at 0 so I dosed it to keep the nitrites alive and within 2 days, it had already skyrocketed back up.

          • If you’re two months into the cycle, the tank should be close to done. Your ammonia is supposed to go down while your nitrites go up, then your nitrites will go down while your nitrates go up. It goes: ammonia to nitrite to nitrate. I would say that if you only have nitrites/nitrates present now, let the remaining nitrites be fixed into nitrates, and then do a significant water change. At that point, your tank should be well cycled.
            Please let me know what your current readings are!

          • I took your advice and let it be for about 3 days and my ammonia is at 0 and my nitrites are almost at 0 as well. My nitrates are at about 30ppm without the water change so I will probably do what you recommended and wait for the rest of the nitrites to convert and then do about a 50% water change. Thank you so much for your help!

  5. Hello!
    I am going to have a nano aquarium (30L). I would like to have some low care plants and some nano fishes or one betta. I am researching from 1 mounth. I have read ca. all your themes. I really appriciate your work, this is the best website I found.
    I have only these question: I cycle the tank, its okay (in the store they offered some bacteria like in this articel I think I will use them) , than I change water before put fishes and plants? and if I change water than the cycle will desappear, and I have to put more bacteria in or a 25-50% water change is a not big deal to the cycle?
    PS: Sorry for my grammer. I am hungarian 21 and not too skilled in english ๐Ÿ™‚

    • Hello!

      Good question, don’t worry about your English. So, luckily, 25-50% water change is not a big deal to the cycle. So there is nothing to worry about, although you can always dose a bit more bacteria after you do it just in case, to strengthen it a bit. You can place plants in the aquarium while you cycle, so you don’t have to wait with that until after. That’s just for the fish.

      Sounds like you have a great plan! I love planted nano tanks. ๐Ÿ™‚ Good luck.

  6. Hi I was wondering if you are still replying to this article I had a few questions about setting up a quarantine tank.

      • Hi ,im just starting to getting into freshwater aquariums ,this is all really confusing ,and im planning on getting a 10 gallon tank with at least one CPO crayfish and some shrimp of some kind and some compatable fish species ,i dont really have any experience in cycling aquariums at all. Can you help me? I think i know that you need bacteria and need ammonia or whatever.

        • Hi Blue,

          The aquarium cycle is very confusing in the beginning, especially since it differs from tank to tank. However, it could be considered the most important part of having a successful tank and should never be rushed.
          Basically during this time, essential bacteria is growing and establishing itself. This bacteria has the ability to convert ammonia (caused by the waste from your tank inhabitants and is toxic if left alone) into nitrite (also toxic) and nitrate (not as toxic if controlled). A cycle is induced by introducing ammonia into the tank and allowing the bacteria to grow until ammonia is 0 ppm, nitrite is 0 ppm, and nitrate is close to 0 ppm; nitrate is actually essential for your system, so you never want exactly 0 ppm.
          There are many ways to introduce ammonia into your system either by way of chemicals, natural organic matter, or materials from another tank; it would be best to Google/YouTube which method would work best for you. You should also pick up a test kit so you can watch your ammonia, nitrite, and nitrate levels rise and fall as the cycle progresses. This process can take up to two months and is usually the time when most beginners make mistakes by rushing into it. If you add fish before this cycle is done, they will die.
          This is a very abbreviated description of an aquarium cycle and there is much more information online that is definitely worth reading into. I hope this helped some.

          Happy fishkeeping!

  7. Hello! Iโ€™m reading a lot of your articles, I have not bought any fish and am not in a position to have any yet but I am very enamoured by all the processes that go into properly maintain and caring for them! Iโ€™m wondering, your talk of cycling the water and getting the ammonia, nitrite and nitrate to appropriate levels is good, but is this also applicable and needed for a pond setting? Iโ€™d imagine it would be, but I just wanted a little extra clarification; the processes of which you cycle the โ€˜tankโ€™ (which I hope for a pond) would they be the same? And, if you were to want to incorporate aquatic plant life, would it be better to have them already situated from the onset of the cycle rather than implemteing them after the levels are cleared?

    • Hey! So nice to hear you’re doing lots of research, you’ll really thank yourself for that later.

      Yes, things are more or less the same when you’re setting up a pond, so the instructions here are applicable to that. Plants can be placed in the tank or pond whenever you’d like. I usually do it right away because in an aquarium setting, planting before flooding the tank is easier than doing so after it’s filled up. The plants don’t suffer from the cycling process. ๐Ÿ™‚

  8. Hi Mari! Thank you so much for your advice on this site. As a first-time betta mom, I want to make sure I do right by my little lady. That being said, Iโ€™m in a small apartment and Iโ€™ve just begun to set up my 3-gallon tank for my betta, who is quite small. Iโ€™ll start the ammonia method tomorrow, and I wanted to ask a few questions:

    (1) Iโ€™ve put API Stress Zyme, Stress Coat, and Quick Start (as well as some aquarium salt, a little amount only, which Iโ€™ll cease doing based on another article I read here). Is that too much? Do I need to pick one or two? I bought a lot of water supplies recently when Iโ€™d noticed she was dealing with clamped fins and I tested high levels of ammonia and nitrites (Iโ€™ve been using Ammo Lock in her bowl while I ready the new tank).

    (2) How big should that ammonia-based aquarium cycle water change be? You mentioned for the food version doing a 90-100% change, and Iโ€™m curious as to whether that just gets rid of the bacteria in the tank. Iโ€™m sure it doesnโ€™t, otherwise you wouldnโ€™t recommend it, but I want to make sure Iโ€™m not compromising my completed cycle.

    Thank you in advance for any guidance you can give me!

    • Hey! Glad to hear the site is helpful to you. Good to hear you’re doing your research ๐Ÿ™‚

      Before I mention anything else, I do want to say that 3 gallons is not my favorite size for Bettas. A tank this small is hard to keep stable, especially if you’re a beginner. I prefer 5 gallons and up – 10 would be my personal ideal size for a Betta! Just a thought.

      As for question 1: I’m not familiar with any of those products, but I think Stress Zyme and Stress Coat are probably similar? Maybe you could pick one of those two. The most important thing though is to do daily water changes with dechlorinated water until you can move the little lady to her new tank.

      Question 2: it mostly depends on your nitrate readings at the end of cycling. You’ll ideally want to bring it down to < 10. For me that usually comes down to a 50% water change. Be sure to also gently clean the filter sponge in a bucket of aquarium water as it might have gotten gunky during the cycling process. Yes, your filter bacteria will take a bit of a hit but it should be fine, they're stronger than most people think. I like to wait 1-2 more days after the water change just to see whether the cycle does anything funky, but it never actually does in my tanks. Hope that answers your questions. If you need to know more feel free to ask. Good luck ๐Ÿ™‚

  9. Hello

    You have left out the easiest way of cycling the tank, and the easier the better for beginners, right?
    That is too fill the tank up, plant it if you have any plants, then leave it
    There is millions if not billions of organisms in the tap water, depening on the tank size, but atleast several millions
    And as you have explained the nitrogen cycle, these organisms start the cycle when decaying.
    I have been doing this for almost 20 years and never lost a fish or a shrimp durring the lack of enough bacteria after the cycle has fullfilled.

    • Funny you say this – it’s common here in The Netherlands to cycle your tank that way as well! I do find it’s a little slower and the cycle is not always as stable starting out. So I personally prefer the ammonia method, but I agree that this way works as well. I’ve done it a few times without noticeable issues, as I tend to stock lightly, especially in the beginning ๐Ÿ™‚ I’ll add a note to the article mentioning it.

  10. Hello. 2 days ago I purchased a 5 gallon tank. 1 betta and 3 guppies. I was told this would work well for this tank. After reading your article which I should have done first…. I realized the tank needed to be cycled first. I was told as long as I used bottle water to fill the tank I wouldn’t need to do anything. Yesterday before work I accidentally dumped too much food in the tank and when I got home it was pretty cloudy. I siphoned out about 1.5 gallons and sucked out the food waste and it does seem better but because it was not cycled I am afraid they will die. They seem healthy but the tank was only set up Sat night and it’s tues morning. What can I do to help the water so they will not die? I’m going to look into a second tank for the guppies since this site states they should not be roomies with the betta but that will take time. They don’t seem stressed. I bought them decorations they can hide in but they don’t use them much. I just don’t want the beauties to die.

    • Hi!

      So sorry to hear you were misinformed, that’s terrible. Glas you’re trying to fix things now, though, I hope it’s not too late yet. If they’re all still doing okay you can hopefully get them through the cycling stage. What you’ll need to do is buy a liquid test kit (there’s a link in this article). Yes, I know they’re more expensive than strips, but they’re also way more accurate and you really need one. If you don’t have one yet you also need to get a filter ASAP. Heater too. Lastly, you’re going to need a water conditioned to remove chlorines and heavy metals from your tap water.

      Then, it’s time for the water changes. I’d say about 25% daily, be sure to match the temperatures. You also check the water daily using the liquid test kit. As soon as you see ammonia or nitrites, do an extra water change. You’ll have to continue doing this until you’re getting nitrate readings but no ammonia or nitrite. Unfortunately due to the water changes this is going to take longer to achieve than it normally would – 6 weeks or more wouldn’t surprise me.

      Again, good job on doing your research and I hope your fish pull through ๐Ÿ™‚ If you need anuy more help feel free to let me know.

  11. Hello from London,UK ๐Ÿ™‚

    We have inherited 2 ordinary goodies in their titchy 20l tank with plastic plants and garish pink gravel.
    They are about 10cm long and healthy but the tank is way too small for them.
    I have bought a new Juwel 120l Lido aquarium with the most impressive folder I have ever seen (has been many year since I kept fish, and back then this sort of tank/filter didn’t even exist).

    Status: I am cycling the new aquarium. It has been 3 days. In it we have a few living plants, aquarium freshwater sand (very well rinsed – took me a whole day!), the new filter, and I treated all the new water with Tetra Aquasafe, so there is no chlorine to damage any beneficial bacteria.
    I have a piece of bogwood and a lovely big root in there too (all fully rinsed in plain water and bought from aquarium shop) in there too.

    This morning, the water is slightly milky in hue, which I am guessing is the new bacterial bloom starting to emerge.
    Since turning there aquarium lights on a few hours ago, the milkiness has gone down.

    The water test I just performed was as follows:
    pH 7.5-8
    Nitrite 0.5
    Nitrate 80
    Water hardness is high – London tap water is, but I have read that goldies are ok with this (their established tank also has roughly the same).

    Today I also put a piece of filter substrate from the established goldie tank, as well as a bit of their dirty gravel, and a plastic plant (!) all of which I am assuming have some beneficial bacteria clinging to them, inside a mesh bag, which is hanging under the surface of the water in the new aquarium.
    I am hoping this will add beneficial bacteria to the environment, which will help the filter along – I am correct?!

    The new aquarium light has been on for about 10 hrs/day so far and the plants look happy.

    Question (sorry, I wanted to give the full picture first!): am I doing everything right? Will adding some of the old tank’s substrate help the cycling process of the new tank?
    I can see the nitrate is currently high – should it be around 40 or less, before I introduce our 2 goldies to their new home?
    Does the nitrite have to be at 0 before the aquarium is ready?

    And lastly (sorry!), can the beneficial bacteria needed to colonise the filter and cycle the aquarium, be present in the new environment via plants etc, without introducing any bacteria like I have done? One fish shop told me that unless I add bacterial startup (quite expensive, from their shop), I will never get the bacteria I need and the other fish shop told me the exact opposite – that I can cycle the water without any seeding required, in 3 days, just with the use of Aquasafe!

    I will keep testing and will not transfer the fish until I am 100% certain they’ll be ok.

    If there is anything else I should be doing, I’d be really grateful for any tips – thank you ๐Ÿ™‚

    • Hi!

      So great to hear you’re really doing your best to give these goldies the best home you can offer! Do keep in mind that they will outgrow this tank pretty soon if they are common goldfish, they are pond fish. You should ideally transfer them to a pond this summer to prevent issues.

      Now as for your questions: it seems like you’re doing everything right and there must already be some cycling action going on in there if you’re seeing nitrites already. Some old tank substrate can help, but filter material usually works best if you really want to kickstart things. It’s not absolutely necessary to add pre-cycled things to your tank, though – see below. It just speeds things up.

      Your nitrites (and ammonia) should be at 0 before you introduce any livestock, both are very toxic. The nitrates should ideally be 20 or less, so you should do a very large water change before you introduce the fish.

      As for your last question, both fish shops were wrong. The beneficial bacteria you need don’t have to be added manually – even if you cycle with no plants or any other added stuff they’ll still multiply and colonize your filter. You just need the ammonia to kickstart the cycle. Some products like Aquasafe help your cycling process but they really won’t get your cycle ready to go in just three days unfortunately.

      All in all, you seem to be doing very well and things should go smoothly if everything continues like this. If you have any more questions, feel free to ask. Good luck! ๐Ÿ™‚

      • Many thanks for replying so fast, Mari.

        It (nearly!) all makes sense except for the large water change bit (before I introduce the goldies)…why do I need a large water change, when at the point of introducing them, the water won’t have had any fish/waste in it yet? Sorry, I don’t understand!

        I did add some filter material, but in my mesh bag, not inside the new filter itself (The Juwel ones are very compact and organised in such a way that I wouldn’t be able to add extra stuff easily).
        Is that still ok?

        Nitrates at less than 20?! My goodness, that’ll take a while…I never imagined I could put them into their new tank after 3 days…but I’m hoping it won’t take months either!!

        Many thanks for your time, Jess ๐Ÿ™‚

        • Hi!

          You do the large water change to remove the nitrates. They don’t lower by themselves – only water changes can lower them, which is necessary as they’re harmful to fish. That being said, in response to your other question, 80ppm is definitely high after 3 days. Have you tested your tap water? Either you’ve added a bit too much ammonia or your tap water nitrates are high, which would be a problem.

          As for the filter material, I think that would work. Putting it in the filter is probably best, but it’ll still be helpful this way.

          I hope this clears up your confusion about the nitrates! As long as your tap water nitrates aren’t super high you can just lower them easily with that large water change, so you don’t have to wait for them to go down. It’s the nitrites that need to be at 0 naturally before you can add fish, not the nitrates.

          good luck ๐Ÿ™‚

          • Thanks Mari – I haven’t added any ammonia (I don’t have any). Apparently I read that our London tap water is a max of 50 ppm of nitrate maximum allowed.
            Yes, I am aware that it is the nitrite and not the nitrate that ought to be at zero, before introducing fish – I am just wondering how my nitrate is 80ppm after 3 days in a fish-less tank, with virtually no ammonia…I guess it’s because the full bacterial cycle hasn’t been set up yet.
            I did what you suggested an managed to find an air gap in my filter, then stuck the old filter substrate into it.
            By the way, is there something I can add to my tank to reduce nitrate at all? In case my tap water is just high all the time and meaning a large water change wouldn’t have the desired effect?
            I looked at the back of my Tetra Aquasafe bottle and it doesn’t seem to do anything to nitrates, only to chlorine etc.
            Thank you again for answering all these questions.
            By the way – I have kept tropical fish before for about 15 years in London and my current goldies are living in the same tap water – there were/are looking very healthy.

          • So you haven’t added any ammonia and your nitrates are at 80ppm? That’s odd. Have you tested the tap water yet? Either it’s that or your nitrate test might not be working correctly – I know some people have reported issues with some nitrate tests as described here, so be sure to look into that. Ammonia is what’s converted into nitrate, so if there isn’t really any ammonia I wouldn’t expect much nitrate unless it’s caused by tap water or a “broken” tes kit.

            There are some things you can use to combat high nitrates. It’s a good idea to use plants; because goldfish will eat most plants, you could try terrestrial plants like Pothos. Just hang a vine in your tank and it will start growing roots and sucking up nitrate soon enough. Just plants likely won’t be enough, though, unfortunately. If your tap water is really that high then you might need to use RO/DI water or try products like Seachem de*nitrate or Purigen. I don’t have experience with those last two but from what I’ve gathered they might be helpful. This will be especially important while the goldfish are still in the tank (hopefully not too long) as their bioload is too large for this water volume and you’re going to be doing lots of water changes and battling those nitrates.

            Hope that helps a little, good luck!

  12. Hi i was wondering if you could help me. I been cycling my tank (29 gallons) since December 24, 2017. I havenโ€™t done many water changes, maybe 3 times, and i am not sure if i am supposed to. Please help me my readings are still showing high nitrates and nitrites and some ammonia. I really donโ€™t know know what to do.

    • Hi! That sounds like a relatively long cycling process, although the water changes might have slowed it – you usually only do a water change at the end unless you’re cycling with fish. How did you start the cycle? The fact that nitrates are present means something is definitely going right, it’s just odd that there’s still ammonia and nitrite present. Did you start it with food? Anything rotting in there can cause ammonia.

  13. I’ve been cycling my tank for about a month. I’ve watched the Ammonia levels go to 0, then the nitrite rise, then go to 0 and the nitrate rise. But now I’m testing my tank and they all say 0. I have no fish in yet but wondering what happened and am I going to have to cycle everything again or is it safe to add fish?

    • Hi! That’s strange. Have you been continuously adding small amounts of ammonia? The bacteria do need new “food” to stay alive. If you haven’t done so yet I would add a bit of ammonia and test after that to see what happens. I suspect you’ll find you still have a cycle going on in these but it’s always good to test.

      Hope that helps! ๐Ÿ™‚

  14. Hello! I just got a betta fish about a week and a half ago and Im having some issues… The first day I brought it home I put him in a temporary tank which was a bowl, the next day I bought him a 2.5g tank and set it up with few decorations and a filter, no heater yet, I immediately put it inside (which from reading this article wasn’t the best idea) but he was doing just fine, he loved his new home and would always swim around and he was eager to eat, three days ago I did his first 25% water change, I used tap water and it was a little warmer thank the water in his tank, I put some conditioner and let it sit for a coupke of minutes while I cleaned the decorations and waste at the bottom of the tank, then I poured the water in and even bought him a heater and changed his food to something better (he had the food that comes with the Aqueon BettaBow 2.5 tank and thought it was bad quality for him) and he liked it the first time he ate it, but the next day I noticed he was less energetic and would not swim around.. He now sits at the bottom of the tank and barely moves.. I probably did something wrong but don’t know how to fix it.. I don’t think is temp shock and today I tried giving him hisnold food but he would spit it out, even the new one, I noticed the water is a little blurrier than before the water change… I feel like the water was cleaner before the change… I do not own a water testing kit, and if I have to cycle the water where could I keep my fish? Help please..

    • Hello! I’m the same person that answered your asks on Tumblr.

      It does definitely sound like the problem is caused by the uncycled tank. 2.5 gallons is, in my opinion, also too small for a Betta and it’s difficult to sustain a stable cycle in these tanks if you’re a beginner. However, it is theoretically possible.

      To get things back in order, order a liquid water test kit that at least contains tests for ammonia, nitrite, nitrate and pH; the Freshwater Master Test Kit is around $20 on Amazon. Having a test kit like this is essential if you want an aquarium. Do large water changes (80-100%) daily while taking care to match the temperature and acclimate the fish VERY carefully until you can start the process below:

      What I would do if I had to cycle while the fish was already there is move the fish to a food-safe (Sterilite) tub and then follow the steps from this article in the main tank. In the mean time, I’d do 90-100% water changes daily or every other day on the tub depending on its size (the larger the better) – again, ACCLIMATE. This is VERY stressful for the fish so do things as carefully as possible. Then, once the main tank is cycled (which you can determine using your liquid test kit), carefully move the fish back in there. Another entirely different option would be fish-in cycling as described at the bottom of this post, but it’s not the method I would go with. In any case, either method is very risky which is why it’s important to cycle beforehand – something many beginning fishkeepers don’t do because no pet store takes the time to tell them it’s necessary.

      Does that all make sense?

      • It does. Although its all very delicate, but I understand and I appreciate the time you take to help me. About how many days would it take for the tank to be cycled? And do I need to add anything to the tank’s water or just let it be?

        • The amount of days it can take varies greatly; it can take up to four weeks or maybe even a little longer if you’re unlucky. You got a bit of a head start so that might help. You don’t have to add anything or do any water changes until the tank has been cycled – besides ammonia, that is (as described in the article).

          Good luck! I hope your fish pulls through.

          • Thank you so much! But Im not sure if I should change the water because I just noticed he’s got fin rot, is not too bad but I don’t want it to continue so Idk what you would recommend me in this case..

  15. Hi there, I recently purchased a blue dwarf crayfish online (can’t be sold in pet stores here in Nevada) and because I have never owned a major aquarium I didn’t really look into the car until it arived. (Not the smartest move) right now it has been in its little bag with a live plant for eating for its second day. I’m not sure if this will end up being bad for him since I started cycling when he arived. There was originally 1 crayfish in my tank before, but only for a day. I checked the ammonia and it is not very high, it’s at a .5. Will it be bad to continue leaving the crayfish in the bag? And if so how long will it take for my tank to be ready? Iv added a very young small amount of fish flanks when I first started cycling and and so added healthy bacteria bought from the pet store and and did one small water change of about 15%-20% of the water.

    • Hi,

      I’d move the crayfish to a food-safe (Sterilite) tub and do regular water changes (frequency depends on the size of the tub) until the main tank is ready. Ammonia will quickly build up in the bag so that’s not ideal at all, especially since cycling can take up to 3-4 weeks. Be sure to cycle as described in this article to make sure the tank is ready as quickly as possible.

      I hope that helps. Good luck!

  16. I have a 150 gallon tank that I’m trying to prepare to set up. TRYING. I plan on getting Orandas.
    I called a local pet store (Petsmart) to find out about cycling and some information about drift wood curing- the lady I spoke with said that if I bought water conditioner I would not need to cycle. Is this the bottled bacteria method of cycling? I know big brand pet stores aren’t the best to get trusty info from but there are no privately owned stores here. Are there any major tips and downfalls to the goldfish varieties? Also what are your thoughts on driftwood vs foe coral for gold fish varieties.

    • Hello! Apologies for the delayed reply, although I assume you’re still in the middle of the cycling process and haven’t bought fish yet. Great to hear you’re doing your research and have gotten a nice big tank. I would definitely try to understock it so the fish have all the room they need to grow. I would personally probably only go for about four goldfish in a 150 gallon.

      The lady in the pet store was very incorrect. Water conditioner is needed to remove harmful chemicals such as chlorine from tap water and some types are indeed effective in removing ammonia as well. However, this is just temporary and not sustainable like actually cycling the tank. You’ll need a product like Quick Start if you want to kickstart the cycle, but even then I definitely wouldn’t recommend adding fish right away.

      As for goldfish varieties, I used to have an oranda but it unfortunately passed away due to swim bladder issues. They are lovely fish but if you get young ones it can be a little difficult to see whether they will end up with a monstrously huge wen. I personally prefer the ones that are a little less extreme! It’s also easier to buy adult fish because there is less chance of hidden issues that come up once the fish ages, but they are definitely a little more expensive. If there’s any possibility to do so, I would avoid buying goldfish from big brand pet stores – the stock is often of bad quality and it’s so discouraging to immediately have to deal with diseases etc. Try finding a local goldfish breeder/importer or a site like Dandy Oranda’s/Raingarden Goldfish, they ship goldfish throughout the US.

      I love driftwood in goldfish tanks, but definitely make sure it has no sharp edges because these fish are mega clumsy. Spider wood, for example may not be ideal, something like Mopani wood is probably a better idea.

      If you haven’t had a look yet be sure to check out the goldfish category here on Aquariadise, there are a few articles in there that might be helpful in your research.

      Good luck! ๐Ÿ™‚

  17. Hi there,
    Would appreciate some advice,
    Have a tank that I set up bought some safe start as it said would cycle my tank immediatly making it safe for fish. Left it 2 days before putting in a couple of guppy. I then bought a test kit it’s been 10 days since fish went in and my test results are ammonia 0.2 (these have dropped from 0.5) nitrite 0.25 ( have also dropped from 0.5) nitrate has stayed at 5 from when I started testing.
    I read online not to do a water change while the tank is cycling with bottled bacteria as it can interrupt the cycle but unsure if these levels are safe for the fish?
    The test kit indicates danger at a higher level but dont want the fish to be uncomfortable, do these results show it’s cycling at all?
    Any advice would be greatly appreciated.
    Kind regards

    • Hello,

      Oh dear, products like safe start do help kick start your cycle but if it says it will instantly cycle your tank that’s not really true. It seems your tank is cycling, but there may not be enough beneficial bacteria to deal with the guppy waste yet (this can also be caused or made worse by a tank that’s too small – at least 15 gallons for guppies!)

      I would definitely start doing water changes. It does disrupt the cycling process, but that’s the annoying part about fish-in cycling: to prevent the fish from getting hurt, you have to constantly disrupt the process which can cause it to take much longer than cycling without fish. I don’t have a fish-in cycling guide, but there is one here (just scroll down to the fish-in cycling part). You’re not in the worst possible situation right now because the tank is already partially cycled, but it could take a while for everything to become stable.

      I hope that helps! Just be sure to cycle your tank beforehand next time, products like safe start can help speed up the process but it’s not a good idea to completely depend on them. ๐Ÿ™‚

      • Hi ok
        I guess it’s a learning curve and I won’t be so niave in future Lol.
        Thanks so much for the advice I will start water changes ASAP, what % and how often would you recommended?

        • It’s definitely a learning curve for every aquarist, such a pity there’s so much bad info out there. I’d suggest sticking with the instructions from the article I linked to – 25% change daily until everything is stable.
          Good luck! ๐Ÿ™‚

    • Hi, been cycling a new setup, 25 gallon low tech planted. I got Ammonia and nitrite readings around day 7,1 ppm and 0.75 ppm respectively. Ammonia dropped to 0 within 2 days and nitrite after 5. Meanwhile I was picking up nitrates at low levels, 0.1-0.3. I did a partial change, 30%, and swished out the filter media. The day after, my ammonia and nitrate readings came back up to 0.5 and 0.4 ppm, and nitrate raised a little also. since then ammonia is back to zero but nitrate remains at 0,25 and nitrates are barely present, < 0.1.

      my questions are –

      1. were my day 7 readings high enough to indicate a cycle?
      2. Did i wash off too many bacteria swishing out, causing the tank to re-cycle?
      3. I did not add fish food or ammonia (oversight) until day 7, but many of the plants were melting and i had a few tiny snails (~10mm). would this have been enough load to cycle?
      4. Since day 7 I have daily dosed with fish food (flake), hoping to build up my colony. Is this sensible?
      5. Finally, I have 2 big, large leaved java fern, 4 large anubias, 4 small pointy leaved crypts and 3 rotala rotundifolia. would these plants likely cause my nitrates to remain so low?
      Thanks so much for any advice on this.

      • Hi!

        It seems things were going well – is there a reason you swished out the filter media? That could indeed wash off bacteria and isn’t necessary during the cycling process. Water changes aren’t necessary either unless you’re cycling with fish.

        Your day 7 readings did indicate cycling, but they were very low and the cycle would probably not have been stable enough to sustain any fish. The melting of your plants and the snail poop likely caused the small ammonia, nitrite and nitrate readings. What you’re doing now, doing with fish food, is a much better plan. You could also switch to dosing with ammonia as described in the article as a less “gross” method. Once you do that you should start to see higher ammonia, nitrite and nitrate readings. The plants will likely suck up quite a bit of nitrate but I think you’ll still get higher readings than before.

        I hope that helps! If I was unclear anywhere feel free to ask any more questions.

  18. If I seed a tank, I can add fish the same day? Asking because I’d like to get my betta into his own tank ASAP so I can medicate him again. He’s in a 15g with some cories rn.

    • Hi! Sorry to hear you’re having problems with your betta. Seeding a tank usually doesn’t instant cycle it unless you move an entire cycled filter to it. I would allow at least a day or two to see to which degree the seeding has been successful and how the water values react (using your liquid water test kit). May I ask what’s wrong with your betta?

  19. Hey I just upgraded to a 10 gallon from my 1 gallon. Unfortunately before I could move my betta he died. I had him for months and just found out his home was too small but it was too late not to mention I cleanse everything without soap which may have killed him. Well now I have a 10 gallon. It’s set up with water, sand, decorations and a hand made rock bridge. I put in aquasafe tap water conditioner and two days later added my snail that was with my betta. When can I add fish and what more is needed for my tank because 1 gallon to 10 is a big jump and I’m lost. 10 gallon was a gift so I didn’t do any research.

    • Hi! Glad to hear you’re doing some research, but sorry about your betta ๐Ÿ™

      The article you commented on contains all the information you need, but I understand it can all be a bit difficult to figure out if you’re not sure what to do yet! You have to get a filter and heater for the 10 gallon if you don’t already have these. They need to be turned on. You also need a liquid drop test kit like the freshwater master test kit, which seems to be most popular in the US. You use the test kit to keep a close eye on the water values and determine when the tank is ready for fish: it’s never the same so I can’t tell you an exact time frame, but it will usually be at least around three weeks. The cycling game then begins! How to cycle is described in the article super detailed, so that should help you. Don’t add any fish until that process has fully finished, or the tank won’t be safe.

      I hope that helps, but if you have any more questions feel free to ask. I listed a few articles below that might be helpful to you. Just keep reading, reading, reading and you’ll figure it out in no time. Be sure to let me know how things go, good luck ๐Ÿ™‚

      How to care for a betta
      Betta tank inspiration
      What aquarium maintenance should you be doing?
      Equipment checklist
      8 easiest aquarium plants

  20. Hi I put two newts in a 5.5 gallon fish tank . I didn’t cycle it sorry didnt know about cycling in till a few weeks ago. So i started to cycle my tank. It has been 12 days . I noticed my small newt always trying to get out buy scratching the glass not climbing on land? Didn’t think much of it. Then 2 days ago my big one starts scratching the glass and climbing on land/rocks. I have 4 1/2″ of water i drop it to 3 1/2″ and fill it back up to 4 1/2″ with reptisafe . Every other day for 12 days. I bought test stripes Walmart only hade stripes no kit. It said ammonia .25 nitrate 0 nitrite 10.0. So i did a half water change then another half change couple hours later.know it saying ammonia .25 nitrate 0 nitrite between 1.0 and 3.0 should i do more? Sorry killed one betta frome cleaning everything no soap with toothbrush. He lasted a year i didn’t now i was killing him. Some of his fines fell off not all put him in shallow dish.scales rased up like bine cone died in 3 days poor guy. I think he liked me little did he know i was killing.

    • Hi,
      There’s a couple things wrong with your setup right now unfortunately. I’m not a newt expert at all, but a 5.5 gallon tank is much too small for them. I would recommend bringing the newts back to the store and then reading up on articles like these before starting with fish/amphibian keeping again! You really need to know how things work beforehand, as just winging it is not a great idea at all when live animals are involved.
      When you’re ready to set up an aquarium again, you can use the 5.5 for small inverts like dwarf shrimp or dwarf crayfish or a single betta fish. Nothing bigger, unfortunately! 5.5 gallons is really, really small.
      Good luck!

      • Well that not to good for my newts . I got them of eBay i cant just send them back . Hope i can just do daily 25% water changes and everything works out.

  21. Hi there
    Iv recently set up my new 60 gallon tank with a used Aqua one 1000 canister filter. New substrate and rocks.
    My question is since I already have about 10 fish I am planning on transferring because of the filter can I add them all straight away or gradually? If so how many and how frequent?

    • Hello! What a coincidence, I’m cycling a 60 gallon with a used canister filter as well. ๐Ÿ™‚
      I don’t know what types of fish you keep, but transferring gradually would be great if the situation allows it! You could split it into three transferring moments with a week in between. As for the frequency, to figure that out you should just keep a close eye on the water levels: if the ammonia levels seem to remain at 0 where they should be, you can add the next “batch” of fish after a week or so. If there are fluctuations, wait until they are over to add more fish.
      I hope that helps a bit!

  22. Hmm, I have a cycled tank already, but would like to move my tank critters (2 guppies and a CPO) to a larger tank (so from 20L to 60L). I added from the brand Tetra, their EasyBalance and AquaSafe to the tap water in the new tank. Do I still have to cycle the tank first? And if I do, can I just put the used filter from the old tank into the new tank in order to get the good bacteria in the new one?

    • You can put the filter from the old tank into the new tank to move the bacteria so you don’t have to cycle. You’ll have to add another filter as well, though, because one meant for a 20L tank won’t be enough for a 60L. Be sure to keep a super close eye on your cycle and do tests with a liquid test kit every day or every other day, because you will likely experience some cycle bumps!
      Good luck ๐Ÿ™‚

      • Thanks for the response!
        I’ve put in the old filter cartridge into the new tank and will wait a few days so hopefully everything will work out!
        (oh, and the new tank came with it’s own filter, so not to worry ๐Ÿ™‚ )

  23. The leaves on my anubias have started to die, and they are rotting in my tank. I didn’t have time to cut them off, so when I tested the water in my aquarium, it had 0.5ppm amonia, and 0ppm nitrite. Since I have no fish in the tank, and already have beneficial bacteria in the tank, would this count as cycling the tank?

    • If you already have beneficial bacteria in your tank I would assume it is already cycled. If not, then this would indeed likely produce some beneficial bacteria. I wouldn’t count it as “cycling”, though, as 0,5ppm ammonia isn’t that much and you wouldn’t have a stable nitrogen cycle.

      • I used bacteria in a bottle which is supposed to make cycling alot faster. I added it on the first day I finished setting up my tank. The water was cloudy from shrimp soil. The media browned in the first couple of days. I only added fish a week later, and when the water was crystal clear. Ammonia was 0.5ppm and Nitrite was 0ppm. It continued to be like that for many days untill one day ammonia became 0. there was never a nitrite reading, ever. I think this is wierd. Is the combination of the rotting plant and shrimp soil
        for the first wek when I wasn’t checking for ammonia or nitrite that provided ammonia to feed the bacteria and keep it alive, and allow the bacteria to settle onto my filter mefrom starving?

        • Interesting that you didn’t get a nitrite reading, although maybe depending on the kind of tests you used something went wrong. If there was “rotting” material in your tank I think that definitely played a role along with the bacteria in a bottle, although I can’t tell you anything for sure! For the tank to have cycled there must have been nitrite, but the test may not have picked it up.

  24. I was thinking about getting a betta and I’ve been researching. That being said, does a tank smaller than five gallons need to be cycled? And if not, why? Thanks!

    • Tanks under 5 gallons do cycle, they just don’t hold the cycle as well: if there’s a single piece of food decomposing in a 10 gallon, it probably won’t be a problem. There is a lot of water to dilute the ammonia that’s released and the larger amount of good bacteria can easily convert it. In a 2,5 gallon, the ammonia concentration will be much higher, there likely aren’t enough good bacteria and nitrite/ammonia spikes will occur. The whole cycle will be off, which can be fatal to your fish.

      Tanks < 5 gallons should be cycled as well, but ideally they shouldn't be used at all because it's so hard to maintain a stable cycle. I'd really recommend you go for at least a 5 gal (if you're worried about the costs, you can get them used really cheap), just to prevent any problems in the future. Experienced fishkeepers can usually keep bettas in slightly smaller tanks, but I personally don’t see why you’d want to. It’s more work, there’s a much higher risk of accidental fish death, it doesn’t look as nice and a 5 gal really doesn’t take up much space at all.

      Hope that clears things up for you! If you’re still interested in getting a betta, this article contains tons of info about proper betta setups. Good luck ๐Ÿ™‚


Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.