Green Hair Algae | Causes, Prevention & Algae Removal




Green Hair Algae

Sharing is caring!

It might start out innocent enough: a thread here, a tuft there.  And then suddenly… a complete algae explosion! Oops.

The dreaded green hair algae is a notoriously fast grower that can take over your tank in just a few days. It suffocates your plants, your fish can get stuck in it, and it looks just plain uglyNo one wants it, but how do you get rid of it?!

Keep reading for everything you need to know about removing (and more importantly, preventing) green hair algae in your aquarium.

Is green hair algae bad?

A healthy aquarium will always have some type of algae in it, the real trick is knowing how to control it if it starts to get out of hand. The problem with algae in an aquarium is that it grows very fast and is very difficult to get rid of once established; most aquarium keepers battle with algae for the first few years of having their tank and even then, an algae bloom may happen at any given time further down the line.

Algae is bad if left untreated; it quickly pulls essential nutrients out of the water column, leaving the rest of your aquatic plants to suffer. Hair algae also has the ability to block out light from fully penetrating the water column and can grow over any aquatic plants in the tank, further suffocating them. If the algae really gets out of control, it has the ability to cause hypoxic water conditions when it dies off, leaving your tank with devastatingly-low oxygen levels.

Most algae are caused by an excess of nutrients, but others actually thrive in aquarium systems with low nutrients; other factors, such as lighting (intensity and spectrum), light period, flow, and CO2 levels, also play a role in contributing to the amount of algae that shows up in your aquarium. The first step in treating algae is by testing your aquarium water and starting to figure out where the root of the problem actually is.

However, it can be difficult to test the water conditions of your tank if your hair algae gets really out of hand. While still a controversial subject among the aquarium community, many believe that algae actually uptakes nutrients faster than can be tested; this means that your tank can have low water nutrient readings or even levels that read zero, but still have an abundance of hair algae. The belief is that the algae is stripping the tank of these nutrients before they can be tested, leading to inaccurate readings. The best way to get accurate readings is by removing as much algae as you can and then repeating the tests.

Green hair algae: Quick fixes

Algae is always annoying, but if you have green hair algae in your planted tank, you might be especially worried. It blocks the light from reaching your plants and sucks up all those important nutrients. It can be tempting to try for a quick fix, but unfortunately, most methods do more harm than good. Here are some common recommendations you may be told that do not actually work:

  • Get some algae eating fish. There are plenty of fish and invertebrates that have a taste for algae, but don’t think that they will solve your problem so quickly. It is never a good idea to just buy a fish for the purpose of troubleshooting an algae problem, especially if it doesn’t fit with the rest of your aquarium stock. You are supposed to fix any issues, not your fish. (Remember: you are the number one member of your cleanup crew!)
  • Try these algae control products. Nope, not the best idea to get rid of the algae in the aquarium either. Although algaecides might work, they don’t actually solve your underlying algae problem; these products just mask it for the time being (and might kill all of your aquatic plants with harsh chemicals in the process).
  • Scrub, scrub, scrub. Before you whip out the algae scrubber and get to work, keep in mind that removing the algae is also just a temporary solution. Although it’s a safer option than algaecides and won’t kill your plants, the problem will just return in a few days or weeks. However, this is usually the best first step to take in discovering the real problem in your tank.

The real problem with green hair algae in your tank

So algae eaters, algaecides, and simple scrubbing won’t solve your green hair algae problem. Why not?

Because green hair algae is caused by an underlying imbalance somewhere in your tank. As long as you don’t solve this by adjusting a few important factors in your aquarium, it might disappear temporarily but it will always return if the main reason isn’t addressed.

So what can you do to solve your green hair algae problem once and for all?

Green hair algae: Solutions

Green hair algae in your planted tank is most likely happening due to one major problem: a CO2 imbalance.

It’s most likely not nitrate or phosphate, but actually CO2. Here are a few easy ways to improve your aquarium water conditions that will lead to the permanent eradication of green hair algae in your aquarium:

  • Start working with CO2. Solve the lack of CO2 by adding a CO2 system if you aren’t using one already. I know it’s pricy and can be intimidating, but it’s a great way to balance things out. When done right, added CO2 will help your aquarium plants reach their full potential and will then easily outcompete the green hair algae.
  • Add more CO2. If you already have your CO2 system up and running, it might be a good idea to check how it operates. Is it still working correctly? Are you adding enough? If not, up the dosage (making sure it’s still safe for your fish) and you might find the algae problem in your tank disappearing or at least lessening within a few weeks. Also, be sure to check if your other macro- and micronutrients are present and balanced.
  • Lessen your lighting. Plants use CO2 when the light is on. If your lights are on for long periods at one time, they will use more. If you lessen the amount of light, they will use less CO2 and other nutrients. More CO2 will be available for each plant during the growing time and algae won’t get the chance to take over. 8 hours of light is the maximum period for lighting with regular strength. If things are really bad, try cutting your lighting cycle in half. A timer can help if you’re not present to turn the lights on and off at the same time every day.
  • Liquid carbon. This is another popular “helper” in the battle against green hair algae. It might not be as efficient in supplying your plants with CO2 as pressurized systems, but it does help. More importantly, green hair algae hates it. Dose a product like Easy Carbo daily as recommended, or even apply it directly to the more badly infested areas.
  • Water circulation. This is an issue in larger tanks and in setups with weaker filter flow. You want the fresh water and the CO2 you’ve added to reach every corner of the tank so all aquarium plants can benefit. Adjust your filter flow or consider a small powerhead if you suspect there are any dead spots where water is not actively flowing.

Other methods

If you are not facing any of the problems listed above, your green hair algae could be feeding off of other nutrients. One big mistake new aquarium keepers often make is the use of regular water when performing a water change. The problem with using tap water or bottled water is that you can’t be entirely sure what is being added to your tank when you make the water change; a lot of tap water contains phosphates and heavy metals that fuel algae growth. Without sending your water out to a laboratory to have it tested for all trace nutrients and elements, there is no way to tell how it is affecting your tank.

The easiest way to solve this problem is by using either distilled water or RODI water when doing a water change. Many supermarkets and pharmacy stores allow you to fill up your own reusable jug or purchase prefilled bottles. These types of water have been treated to remove any unwanted nutrients or elements that could be causing the green hair algae to grow in your tank.

Another common problem that leads to green hair algae growth is overfeeding; underfeeding can also cause your tank to have algae, but you are more likely to experience other aquarium algae types that thrive in low nutrient conditions. The solution to this is easy: stop fueling your tank with so many excess nutrients. Many foods are very high in protein and your fish don’t actually need that much. While the amount you should feed changes from tank to tank, this could be a very easy solution to get rid of hair algae.


The conclusion: green hair algae is most likely caused by a CO2 imbalance in the water parameters of your tank. Fix the CO2 imbalance by adding more or decreasing the demand, and you should start seeing improvements over the course of a few weeks. Of course, you can and should combine this “treatment” with regular scrubbing and hair algae removal. After all, you don’t want to look at a hairy green tank until the positive changes take their effect!

Also try increasing water circulation, adjusting your lighting (period, spectrum, and intensity), changing the water you add to your tank, and monitoring how much food you give. It is a very long and labor-intensive process to completely get rid of the algae of your tank and it will never be perfect, but it’s definitely better to deal with it sooner rather than later!

An important note: If you’ve never worked with pressurized CO2 before, research it thoroughly before you start. Too much CO2 can be fatal to your fish. Also be careful with liquid CO2, especially if you’re choosing to overdose. Although it’s less easy to overdo it, some plants and invertebrates might react badly to it.

If you have any more questions about green hair algae in planted tanks or if you want to share your own tips and tricks, don’t hesitate to leave a comment below!

Sharing is caring!

10 thoughts on “Green Hair Algae | Causes, Prevention & Algae Removal”

  1. I have a 10gal tank that I want to eventually to house neocardina again. I restarted this tank ~1 month ago after having given up on trying to solve the green algae beast on this tank started over 2 years. Dumped everything from old tank, so using all new stuff inside. That means restarting the nitrogen cycle again. Using a mixture of flourite and fluval plant/shrimp stratum with a wide variety of plants (heavily planted with ~11 different varieties including a floating variety to shade part of the tank for the low light varieties). I’m doing a slow restart using only plants to cycle this tank. I did use a bacteria restart ( Stability) and my numbers are still fluctuating where the ammonia is around .25ppm and nitrates at 10-20ppm. Nitrite is 0. GH is 7 and KH is 1. I didn’t want to buy an active CO2 system and opted to try the passive CO2 system from Fluval since it is a small tank. The first tank had no CO2 system and I used Excel for my CO2 needs. I never could get the algae under control. I’ve tried the lower light schedule at 7hrs and then a 4hr on/1.5hr off/ 4hr on/ 15hr off. I have a LED light strip that is 2yrs old and seems just as bright. I just added fert tabs to the soil and was thinking of adding flourish liquid fert (not sure if too soon to add- plants are not necessarily established – last one planted ~1week ago) to support the floaters and to add micronutrients.

    I am NOW seeing the beginnings of the green hair algae again!

    I have a CO2 checker and it never turns green even hours after the CO2 has dissipated from the chambers. I refill the chambers twice daily. Plants look GREAT and pearl (never saw that with my first planted tank). I do 25% water changes with RO water every 10ish days. The light cycle is back to that 4hrs on/off thing I mentioned above.

    Could the cycling of the tank be the cause? Any other suggestions to try before this gets way out of hand?? I don’t plan to add any animals until my test numbers show the cycling is finally stable…

    Thank you for taking the time to read all this! I really would appreciate any suggestions to stop this hair algae. The tank looks so pretty right now and all the plants look very healthy…

    • Hi Susan!
      Well it definitely sounds like you know what you’re doing but your tank just doesn’t care :-). Oh the joys of this hobby.
      It’s very strange that you’re experiencing algae with floating plants; usually, they suck up everything until they overpopulate and the balance goes out of whack again.
      Hm.. quite the headscratcher. I have a few ideas. One, you are dosing too much. You may have overloaded the system with the Stability and root tabs. Two, your lighting is the wrong spectrum/malfunctioning. I also don’t think the staggered photoperiod is helping too much; I think you’re much better off just doing a strict 7-8 hour period. Three, maybe your RO system is malfunctioning/needs a new filter/etc.; make sure to test your parameters from there. These are my main ideas.
      Yes, the cycling of the tank is probably the culprit here, but it could be exacerbated by the factors I mentioned above too. I would try to remove as much of the algae as you can by hand. Maybe bump your water changes up to once every week; it gets tricky here because you want to still have nutrients leftover for your plants, though you should be getting some from the tabs. I would also look into introducing a fast-growing plant or floating plant (like duckweed) that won’t hurt to be removed later on, just to start moving towards a balance.
      Hopefully, your parameters start working with you so that you can start adding snails and a cleanup crew! I hope the algae leaves your tank soon. Let us know how things go.

  2. Hi! I don’t run C02 as it’s a low tech freshwater 10 gallon aquarium. Do I still need to run C02 to get rid of the green hair algae or is there something else I can do?

    • Hi! As described in the article, the alternative would be decreasing your lighting cycle: if you can’t add more Co2, you have to decrease the demand for it. Good luck!

    • Yup, for sure. If there’s no plants to outcompete the algae and absorb all the Co2 and nutrients you’re gonna have a problem.

  3. Hi guys

    awesome information.

    i am struggling with hair algae to the point of depression 🙁

    I have a tank in the wall that measures 1.2m wide by 1m tall and .3m deep. I have white pearl sand, live sand i believe it is, with live rock at either end and a small area in the middle with nothing ( i used to have live rock there and this was the main rock that had hair algae on it so i removed it believing it was leaching phosphates). Now the rocks at either end are covered in hair algae only the side which is facing the large windows which measure 3.6m x 1.5m each and these provide allot of natural daylight the other side of the tank faces the hall way and does not have much exposure to natural light. sitting on top of the tank is a LED light which i purchased from ebay has two settings blue and white light or just blue light.

    I have only a clown fish, 3 chromis, goppi, turbo snail, had a damsil and a royal grammar these passed away.

    i do get the algae film on the glass also this can easily be cleaned with a magnetic cleaner.

    i feed the fish two times a day and i feed them patiently ie make sure all the food is consumed before adding more its frozen shrimp. so i am pretty sure food is not decaying in the tank.

    I have a external water filter with a uv light which i leave on

    I only use RO water. i have had the water tested a few times every time the levels are perfect i have a home kit and measured at home also (everything but phosphate) and again all seems good.

    I dont have any plants or corals other than some coral which has spread by itself long tentacle type white / brown colour this is because again i am patient and luckily children are also wanted to make sure the tank was happy before adding the expensive stuff

    flow seems pretty good as the corals tentacles move around a fair bit not sure how scientific that is.

    If more information is needed i can provide.

    I have not measured CO2 as this is the first i have heard of it to be honest.

    Forgive any mistakes i am a beginner and any thoughts would be greatly appreciated.

    I did try adding a sea hare but it lasted only 2 weeks and did not eat all that much i was contemplating a tail spot blenny but i always prefer rectifying rather than knee jerk solutions if at all possible but he looks like a cool fish may add hoping he can trim this algae down.

    • Hey! Aquariadise centers around freshwater aquariums and I have no experience whatsoever with marine tanks, so I have no idea whether there are factors in marine setups that cause hair algae to appear besides the regular factor of light. So the only thing I can ask is: have you had a close look at your lighting cycle yet? Natural light from windows can be problematic if it’s direct sun. And how long are you leaving the light on for? I’d see how that compares to what other marine aquarists are doing.

      Sorry I can’t be of more help, I hope you’re eventually able to figure it out! Good luck 🙂

  4. Thanks! for such a well written clear and accurate piece of advice. It has tought me a couple of things and confirmed a few things too.

    I too battled the green hair algae and certainly found ‘algae killers’ to be of less than no use.
    In my case I managed to get rid of it without co2. I removed the largest concentrations of it from my tank (sadly it meant my java moss had to go) and then loaded my external canister filter with coal ( generally used for removing unwanted chemicals) and that fixed it. ( I also did less than a quarter water change). No algae issues at all in the past 3 years 🙂


Leave a Comment

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