How to set up a quarantine tank

Quarantining newly purchased fish is so important as we can’t see if they are carrying parasites with the naked eye. Set up another tank to introduce fish to first and you’ll have a chance to properly acclimate them, get them feeding and rested, identify any health problems and treat disease if necessary. A quarantine tank can double-up as a hospital tank or even a breeding tank too. Here’s what you need:


A quarantine tank doesn’t need to be large and a 60cm aquarium will be fine to quarantine most fish up to 4” in length. It doesn’t need to be luxurious either so pick function over form. It does need a tight-fitting lid however as newly purchased fish are very prone to jumping. A bare tank and hood are all you need to get started. 


Use an air-powered sponge filter or a small internal power filter, but mature the sponge in your main tank for a few weeks beforehand. Water quality issues are common in quarantine tanks as typically they are set up in haste and without a mature filter. Even low levels of ammonia or nitrite can push a stressed or diseased fish over the edge so mature the filter to eliminate any risks. Test for ammonia and nitrite on a daily basis. 


Choose a simple heater/thermostat to warm the water, but check the temperature with a separate thermometer. Heat can be used to help combat Whitespot by turning the temperature up as high as 30C, so make sure that temperature is within your heater’s (and your fish’s) range. To select the right heater you need one watt per litre of tank water. So a 50 litre quarantine tank requires a 50 watt heater, in most homes. 

aquael in the box
A simple quarantine tank just needs a heater, a filter, and a lid.


You don’t actually need a light in your quarantine tank as bright light can stress new fish. Most tank set ups do come with built in lighting however so leave the light off or just put it on to closely inspect the fish. If building your own quarantine system you could choose an under-powered light like a small LED to just provide very subtle lighting. 


Quarantine tanks and hospital tanks should not contain any substrate materials as some parasite lifecycles involve a substrate dwelling stage. So go bare bottom but to cut the glare out and make the fish feel a little more comfortable, paint the underside of the tank base black or site the tank on a dark surface.

Some species will be stressed if they can’t hide though so add some pieces of cut plastic pipe that the fish can fit into, or a flowerpot. A plastic plant can be used to.  

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Jeremy Gay is an author, lifelong fishkeeper, and aquatic specialist. He's a former editor of Practical Fishkeeping Magazine, UK editor at Reefbuilders, a former aquatic store manager, and has collected fish in Sri Lanka and the Amazon. He's been on tv and radio, contributed to Koi Carp and Gardeners World magazines, been a product tester, a judge, and a product developer. Jeremy is here to guide and advise you on all things tropical, pond and marine, from set-up to stocking, health, feeding to breeding, as well as solving many common fishkeeping problems along the way.

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