Articles Fish disease

Quarantine tank 101 – What is a quarantine tank?

June 8, 2013
quarantine aquarium

Although quarantining fish in a separate tank or tub whenever it’s needed can prevent disease from spreading in the main aquarium, it’s something that’s often forgotten or skipped by impatient fishkeepers. I started using quarantine tanks a while ago, and it has saved me a lot of worrying and stress. And it doesn’t have to be expensive or time-consuming at all!

When should a fish go into quarantine?

Quarantine tanks and tubs are usually set up when a new fish (or group of fish) has just been bought. Because you can’t be sure whether these new fish are sick or not, as some diseases take a while to become visible, the fish are put in the quarantine tank for 2-6 weeks and observed until you’re 100% sure they’re healthy. When dealing with bigger fish, a microscopic examination is often done during the quarantine period in order to rule out parasites. With some types of fish (puffer fish, for example) it is recommended to always treat for worms/parasites during a quarantine period before introducing them to the main tank.

By observing a quarantine period the fish in your main aquarium won’t be at risk of disease from the new fish and it’s easier to treat with salt/medication if your new additions do turn out to be carrying a disease or parasite.

Another good moment to set up a quarantine tank is if you have a fish with a disease or parasite that is not contagious and does not spread through the entire aquarium. Examples of this are fin rot, pop eye, dropsy, etc.
When this happens, don’t treat the entire main aquarium! It’s a much better idea to set up a quarantine tank for that one sick fish and treat it in there. That way you protect the rest of your fish from unnecessary medication and you can keep an eye on the sick fish more easily. It also protects the sick fish, which will be weaker than usual, from curious fin-nipping tankmates and it will help you monitor its food intake. When it has recovered completely, it can return to the main aquarium.

betta injury

A fish with an injury like this can be moved to a quarantine tank for treatment.

Advantages of a quarantine period:

There are many different factors that make a proper quarantine period important:

  • If a new fish is sick, it won’t infect the rest of your aquarium and your (often expensive) fish!
  • Quarantine tanks are usually smaller, which means you don’t have to use as much medication for each treatment – much cheaper in the end.
  • Heavy medication such as antibiotics can destroy the cycle in your main aquarium but are harmless in a quarantine tank.
  • Unnecessarily treating the whole main aquarium means weakening all fish and contributing to resistant bacteria strains.
  • During the quarantine period, fish can adjust and gain a bit of strength before having to compete for food with others in the main tank.

Conclusion: always having a quarantine tank or tub ready is a must! If you’re wondering which equipment is needed for a quarantine tank and how to keep things as cost-efficient as possible, have a look at Part 2: How to set up a quarantine tank.

If you have any questions about quarantining fish or if you’ve got something to add to this article, don’t hesitate to leave a comment below. Happy fishkeeping!

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  • Reply Alvin Yao October 3, 2014 at 4:19 am

    Where do you buy plastic food safe storage tubs? I want to use them as a main aquarium, as they are much cheaper than glass or acrylic ones. Is there such thing as a 600 L food safe storage storage tub?
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    • Reply Mari October 3, 2014 at 11:10 am

      I think with that size you’re looking at a stock pond. I had my goldfish in one for the summer last year.

      • Reply Alvin Yao October 3, 2014 at 2:48 pm

        Is a 80L clear plastic under bed storage tub safe for aquarium use? The one I’m looking at is made of random copolymers, is that aquarium safe? I’ve seen other people use plastic underbed storage containers as aquariums, but I’m not sure. This storage container has the dimensions of: W:50cm H:17.8cm L:100cm and has a volume of 80L. It has a lid and also wheels on the bottom

        • Reply Alexey October 3, 2014 at 3:01 pm

          Hey Alvin Yao,

          It is not what polymers tube made of what makes it food safe, it is which polymerization initiators were used. You will never find which one were used in particular plastic product, but it is quite easy to tell whether the plastic is food safe or not by special symbol with fork and glass, which usually is on the bottom.

          • Alvin Yao October 3, 2014 at 4:05 pm

            Thanks for your reply!

          • Alvin Yao October 3, 2014 at 4:08 pm

            I still can’t find large food storage containers though, all I can find are tiny maximum 8L food containers.

          • Alvin Yao October 3, 2014 at 4:18 pm

            also… I saw this video:

          • Alvin Yao October 4, 2014 at 9:58 am

            Yay found a 140L clear plastic tub made from 100% food grade plastic.

  • Reply Alexey September 17, 2014 at 3:03 pm

    Hello, Mari!
    Thank you for the useful advice.
    As I am beginner and just starting my first aquarium, I have couple of stupid questions:
    1) when there are nobody in tank yet (only bacteria, plants and several hitchhiked baby snails), should I also quarantine the very first fish which come to it?
    2) when I buy group of small shoaling fish, should I quarantine them all together or set up several smaller individual quarantine tanks for them?
    3) Isn’t six weeks too long time for the fish to live without extended ecosystem (plants, bacteria, etc.)?
    4) What are the rules for a) plant and b) invertebrate (snails, shrimps, crayfish) quarantine?

    • Reply Mari September 17, 2014 at 7:38 pm

      Hi! Glad this article was useful to you.
      It’s a good idea to still quarantine the first fish you put into your aquarium, especially if you already suspect they may be carrying a disease. Fish medication can kill the good bacteria in your filter, which means that if you put the fish in the tank and then find out they have a disease, you may damage the cycle. If the possibility of cycle bumps is not a problem for you then you can put the first fish straight into the main tank.
      All fish that are bought from the same water system can be quarantined together. Shoaling fish come from the same aquarium store tank, which means there’s no use in quarantining them separately!
      Six weeks is a very long quarantine period, although it is done sometimes, which is why I mentioned it in the article. I know some HQ fancy goldfish importers quarantine their fish for that long because the fish are very expensive and they can’t risk contamination. They do, however, usually have an automatic water change system. This means there is no cycle necessary as the fish are constantly supplied with fresh water.
      If you want to ‘quarantine’ your plants, which a lot of people do because they may be carrying pest snails, you can do a bleach dip with diluted (1:8-1:10) bleach to kill any unwanted organisms. If the plants are too fragile for that, you can also put them in a bucket with water and keep a close eye on them to see if anything unwanted comes out of them.
      If I add inverts I quarantine them the same way I do fish, although it’s harder to see if they’re carrying disease. To put it bluntly, if they’re not dead after 2-3 weeks I usually deem it safe to add them to the main tank, haha… 😀

      Sorry about the wall of text, but I hope this answers all your questions! Good luck!

      • Reply Alexey September 18, 2014 at 12:00 pm

        Thank you very much for you answer! I will follow your recommendations.

  • Reply Izzy the Fish Girl June 9, 2013 at 5:02 pm

    Mari is totally right. It’s something you never really understand until it bites you in the butt. I brought in fish lice and ich on a fish I didn’t QT. I learned my lesson early. I personally know people who have brought in other terrible things like calumnious worms and bacteria infections that can wipe out a fishroom in days. I don’t mean to scare anyone; I just want you to be careful. Even the best fish stores can get infections.

    • Reply Mari June 10, 2013 at 5:31 pm

      Exactly! Even your absolute favourite super trustworthy aquarium store can get a bad batch of fish in, or fish that are just so stressed out from shipping that it has made them ill. Taking the right safety precautions can really save your entire tank!

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