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Quarantine tank 101 – What is a quarantine tank?

Last Updated January 23, 2020
quarantine tank

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 use simple, cheap food-safe tubs 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 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.

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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