Quarantine Tank

It is very important to place a new fish into a quarantine tank for 4 to 6 weeks before introducing it to the main display with other healthy fish. Even if the new fish appears healthy, it could still be carrying disease, either from the wild or from the stress of shipping.

If a new fish is carrying a disease but not showing obvious signs just yet, there is a risk of every healthy fish in the main display tank getting infected. I have seen entire fish tank populations get wiped out from marine ich (Cryptocaryon irritans), velvet (Amyloodynium), and Brooklynella because of the lack of proper quarantine procedure! These diseases infect the gills and skin of fish and, if untreated, usually results in death in 2 or 3 days.

Another good reason for quarantining fish is that most have journeyed thousands of miles before being placed into the dealer’s tanks. Recently transported fish are in a weakened state and to add such fish to a tank of robust, healthy fish will usually mean that the newcomers will take to hiding for several days and be unable to feed or fend off harrassment by other fish.

Quarantining helps these new fish to feed and gain back their strength.

How To Set Up A Quarantine Tank

A quarantine tank doesn’t need to be fancy. All you will need is a cheap glass or acrylic tank between 10 to 15 gallons. For larger fish such as tangs or large angelfish, a 30-inch long, 30 gallon quarantine tank should suffice.

The quarantine tank should be undecorated, with no live rock, sand or gravel. Having live rock or live sand in the quarantine tank will mean that medicating the fish, should it be required, will kill off organisms on the rock and sand, resulting in an ammonia spike.

A few rings of cut PVC pipe can act as a hiding place for the fish to give it a sense of security. Ambient light from the room during the day is adequate enough lighting for the period of quarantine.

quarantine tank

Quarantine tank for new fish

Water for your quarantine tank can either be newly made saltwater or saltwater from your main display tank. I prefer to fill quarantine tanks with water from my main display tank as that is what the fish will make its home in eventually.

Most importantly, a piece of filter sponge or foam that has been left in your main tank for a couple of weeks should be placed in the quarantine tank. This is to provide the tank with a source of nitrifying bacteria so that ammonia produced by the fish can be broken down quickly to nitrate. An Ammonia Alert badge is also very useful for monitoring for ammonia.

I use a small hang-on-back power filter to aerate the water although a simple air pump and airstone would also suffice. If you are worried about the water not getting enough oxygen, use both a power filter and air pump.

Monitor the temperature in your quarantine tank with a thermometer — a  good temperature range for a quarantine tank should be between 26 to 28 degree C.

Use a heater if it gets too cold and a cooling fan to increase evaporation if the tank tends to run too hot. But be sure to monitor the water level on a daily basis! Too much evaporation in a small body of water such as a 10 gallon tank leads to increased salinity.

A quarantine tank needs to be set up only when you plan to use it to quarantine newcomers. After the fish complete their quarantine, the tank can be emptied, cleaned and stored away.

Introducing Fish To The Quarantine Tank

It is very important to acclimate the fish slowly to the water in the quarantine tank to avoid osmotic shock. Osmotic shock results when a fish is not gradually acclimated to the water in its new surroundings and there is a difference in pH between the water in the shipping bag and water in the quarantine tank.

Some aquarists routinely subject the fish to a hyposalinity or freshwater dip before acclimating them for the quarantine tank. This is completely unnecessary and only subjects the fish to extreme stress!

Freshwater dips should only be used when the fish has developed obvious signs of disease like ich, in which case a freshwater dip may be necessary to save its life.

How Long Should You Quarantine New Fish?

The life cycle of parasites that cause diseases like marine ich is approximately 6 weeks or 40 days. Realistically, to keep your main display tank ich-free, all new fish should be quarantined for the full 6 weeks during which time they should appear disease-free.

If the quarantined fish is indeed infected, the symptoms of the disease will have appeared during this time period and the fish can be treated accordingly. Medicate diseased fish in the quarantine tank. Once the fish recovers and no longer shows signs of disease, the quarantine period should be extended for a further 6 weeks.

Feeding Fish In Quarantine

It is normal for some fish to hide for the first couple of days in quarantine. Feed very sparingly during this time as the fish may not come out to eat at all. It is best to walk away from the quarantine tank after dropping a few morsels of food into the water to encourage the fish to come out and eat. Carefully siphon any leftover food as it will foul the water and lead to a possible ammonia spike.

Once the fish has gotten used to its surroundings, feed once a day and only as much as the fish will consume. And avoid feeding flake foods to a quarantine tank as it tends to pollute the water very quickly.

Soaking food like thawed mysis or dry pellets soaked in Garlic Guard will help to boost the fish’s immune system.

Quarantine Tank | Water Changes

It is a good idea to change 10% of the water in the quarantine tank every 3 days. This helps prevent the buildup of ammonia which could kill the fish. Again, I prefer to use the water from my main display tank for this purpose, replacing the water in the main display with newly made saltwater, of course.

Remember that the quarantine tank does not have a mature biological filter and it should be treated with care as far as regular water changes and careful feeding.

Read more about Aquarium Livestock:

How To Acclimate Fish

Feeding Marine Fish

Mandarin Fish | Care and Feeding

Aggressive Fish

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