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Setting Up a Temporary Quarantine Tank
A small investment of time and money in a simple quarantine tank can pay for itself many times over!

 Age of Aquariums > Aquarium Articles


A Quarantine Tank (QT) is a very useful and important accessory for the serious and responsible aquarist. But one of the pitfalls of setting up a QT is that it often ends up as another fish tank, and then when you need it, there is no place to quarantine fish! Also, some people just don't have the space to keep a QT running all the time. For this reason, it is helpful to have a system that can be taken down, cleaned and stored between uses, then easily set up again whenever needed.

There are three main uses for the QT:

(1) Quarantine for new fish
When adding new fish to an established community, it is best to quarantine the new fish for at least two weeks prior to introducing them into the main aquarium. If the new fish have parasites or diseases, they can be diagnosed and treated, preventing the introduction of harmful organisms into the main aquarium. Some people will treat all new fish with an anti-parasitic medication even when no symptoms are present, much in the same way that cats and dogs are routinely dewormed. Wild-caught fish are very likely to have parasites but show no symptoms, and may infect the less-robust domestic-bred fish which can quickly be overcome. Or the wild-caught fish may not have been exposed to pathogens the domestic fish carry and may be overcome. It is especially important to quarantine new fish when they are intended for a tank already containing valuable fish, which would be difficult to replace. Live plants may also be quarantined to help prevent the infestation of snails and other harmful organisms.

(2) Medical use
When fish are sick or injured, it is sometimes better to remove them to a hospital tank and treat them separately from the main community, if the main community is not affected by the illness. The QT is usually smaller than the main tank as well. This makes it more economical to treat sick fish, as medication for a 40 liter tank is less costly than medication for a 200 liter tank. Also, many times there are invertebrates in the main tank which may be harmed by some medications used to treat fish. In the case where medication is needed for the main tank, the inverts can be removed to the QT for the duration of the treatment, then safely returned after the treatment course and all medications have been removed.

(3) Breeding/Fry care
When you want to breed your fish they may need to be separated from the main tank into a breeding tank, where the fish can be conditioned for breeding and the water conditions can be manipulated to induce spawning. The parents often must be returned to the community as soon as eggs are laid so that the eggs or fry are not eaten. The eggs may need anti-fungal medication; the fry may need special fry food, special water conditions, and a little time to grow. Later a separate, larger ‘grow-out’ tank may be employed as the fry continue to gain size.

Setting Up and Using Your Quarantine Tank

The following items are needed for setting up your QT:

  • Aquarium - 40 liters is recommended for average fish (up to 10 cm). Medicating is very easy in a tank this size because of the dosing amounts, but of course each case must be analyzed individually. If your fish are large or if you have many of them, you will need a larger size for your QT. On the other hand, a betta may be quarantined in a 4 liter jar.

  • Water - Fill the tank with fresh, clean water from the same source that you use for your main tank. Condition with the same products you use for your main tank, and adjust the temperature to approximate that of your main tank. If you will be changing the water conditions for breeding purposes, do it gradually (or as directed), after the fish have been introduced into the QT.

  • Heater - the temperature for a QT can be controlled with the use of a heater. A fully submersible heater is recommended.

  • Thermometer - to monitor temperature.

  • Filter - A simple sponge filter or hang-on power filter is sufficient. The sponge is best for small fry or delicate fish that do not do well with much current. Another inexpensive and effective option is a power head with a micro-filter such as Hagen Quick Filter attached. This filter removes particles down to 1 micron which is very useful to help clear away parasites. A power head with an adjustable flow rate is ideal. To ‘instant cycle’ your QT, add some of the biofilm collected from your main tank’s filter. This is the brown slime that builds up on the inside surfaces of your filter and intake tubes, and is where your nitrifying bacteria reside. You can just collect some and put it in the water of your QT and immediately add the fish. The bacteria will be taken up by the filter and immediately go to work for you.

  • Ammonia Monitor - To ensure that you have added enough biofilm, check for ammonia. An ammonia monitor such as Seachem Ammonia Alert is very useful as it remains in the tank and any color change alerts you to an ammonia problem before it gets serious. If you notice even a slight color change, simply add more biofilm from the main tank. This is adequate for most quarantine situations. Certain medications will destroy nitrifying bacteria so a different approach needs to be taken if you need this kind of medication (the packaging will usually tell you if it harms the nitrifying bacteria). In such a case, it would be better to monitor ammonia with a salycilate test kit and use an ammonia neutralizer such as AmQuel Plus, as needed to detoxify any ammonia that may appear.

  • Decorations - To feel secure, most fish need a place to hide. Some kinds of fish would prefer a cave of some sort, others would do better with plants. Having a cave and both floating and suction-bottom plastic or silk plants would provide adequate cover for most fishes, reducing stress. You can convert any plastic plant to suction-bottom plants by removing the plastic bottom and attaching it to the suction cups that are available at aquarium supply shops or hardware stores. The plants can then be attached to the floor of the aquarium and stay put. If you are breeding fish, you will need to use whatever is appropriate for the fish such as a spawning mop or some live floating or potted plants...whatever the fish needs for breeding.

  • Cover and lighting - A cover is essential to maintain temperature stability, reduce evaporation, minimize dust and airborne pollutants, and prevent the loss of fish that may be inclined to jump. Lights are essential for plants, optional for fish, but it is easier to examine your fish with lights. To reduce stress with sick or light-sensitive fish, the lights (if used) can be left off most of the time, and turned on just for feeding and examination.

  • Forget the Gravel - gravel is not necessary for a QT, and is not recommended. Omitting gravel makes the QT easier to clean both during and after use, and easier to store.

    With a simple, non-medicated quarantine for new fish or breeding/fry care, just do the regular water changes according to the schedule you would normally use, and when the quarantine period is over, acclimate the new fish to the main tank.

    For sick or injured fish, breeding and fry care, follow any recommendations for medicating if needed and water changes as directed. At the end of the treatment, do water changes and chemical filtration (i.e., carbon) as needed to clear the water of residual medicine, then acclimate the fish to the main tank as you would when adding new fish.

    Depending on what kinds of illness or medications (if any) were used in the QT, cleaning can be as simple as a good rinsing and drying, or you can use vinegar or a dilute bleach solution, and a little time in the sun to kill suspected pathogens. Always rinse all parts well both before and after each use. Dry completely before storage to prevent mildew.

    Happy Fishkeeping!

    Reader Comments Comment

    I have had a 260 L Vincenza L.E. marine tank for eight months and I'm new to the hobby. My tank has gone through its cycle, put my clean up crew in turbo snails hermit crabs and added my first fish, everything was great. I would just like to say to all you good people I then made my first and worst mistake: I hurried to get my next fish, a copperband butterfly, not doing my homework. I did not have Q.T. tank. Big problem, my copperband had Ich and infected all the fish I added to my tank. To beginners: always get a quarantine tank before you get your main tank and read up about the most common infections in marine fish before you start. For me the challenge of reading and getting it correct will be a pleasure as I wont be derailed from such a beautiful hobby. I would just like to say this site has given me the best information regarding quarantine, thank you.

    Contributed by Gerard McGivern

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