Quarantine Tank

It’s a fact that if you want to be a successful aquarium hobbyist, you must make room for a quarantine tank in your hobby. Quarantine tanks are essential to treating your sick fish and keeping your healthy fish healthy. So, how do you make a quarantine tank?


A quarantine tank (sometimes called a hospital tank) doesn’t need to be overly large. A tank that holds 5 to 10 gallons is considered adequate for a quarantine tank.

Buckets, plastic, and any non-metal containers that are clean can also be used as a quarantine tank. You also do not need to replicate your main tank and buy everything you have in your existing aquarium tank to make your hospital tank.

It doesn’t need to be fancy and expensive. The barest minimum aquarium set-up will already effectively serve the purpose of a quarantine tank. To set it up, you’ll need:

Air pump and Airstone
Test kits



A secondary filter that you’re already using in your fish tank can be used as your quarantine tank filter. If you don’t have one, buying and using it in your tank as a secondary filter until you need it for your quarantine tank will also be wise and cost-effective. Just be sure to change the media and clean it thoroughly. Cycle the new media, if possible, before reintroducing the quarantine filter into your tank.

Alternately, you can use a dedicated filter for your quarantine tank. A simple sponge filter will do. A power filter is not recommended, especially for very weakfish, as the noise can stress them out even more.

And remember, activated carbon in your filter strips your aquarium of chemicals and medications. Thus, you must remove the carbon from the filter. Otherwise, your drugs and treatments will all be useless.


Make sure to use an adequately sized heater for the size of your tank.


Again, your air pump doesn’t need to be expensive. A simple air pump and some air stones to increase aeration will do.


You’ll need fishnets to transfer your sick fish from your aquarium to your quarantine tank, but it’s wise not to use the same fishnets you regularly use for your aquarium and healthy fish. Use a separate fishnet.


To make the transfer less stressful for your fish, you’ll need to match the pH level and the temperature of your aquarium to that of the quarantine tank. After the transfer, there’s no need to match both tanks’ temperature, and pH levels as both will naturally have different pH and temperature after a few days.

You will also need water test kits when you’re performing water changes in your quarantine. The new water should match the temperature and pH level of the old water. Otherwise, your stressed fish will get even more stressed dealing with all those changes.

Of course, before transferring your sick fish to the quarantine tank, you will want to test for ammonia, nitrite, and nitrate too.

It’s easy (and significantly inexpensive) to make a quarantine tank. When you’ve already gathered all the equipment you need, then you’re down to setting it up and then making sure you use it effectively.

Here’s how you can set up your quarantine tank.

Quarantine Betta Fish
Quarantined Betta (Sick) Fish


1. Get all the equipment for setting up a quarantine tank.

2. Clean everything thoroughly (from tank to aquarium accessories) with hot water. Like when you’re cleaning your aquarium, do not use any soap or chemicals when cleaning and preparing your quarantine tank.

3. Set up your tank and fill it up with water from your main aquarium. You’d want the sick fish to acclimatize quickly and feel comfortable with his new surroundings as much as possible. You can help do that by using the same water from your main tank. This will also ensure the water’s temperature, and pH levels in your aquarium are the same as your quarantine tank.

Note that after you have transferred your sick fish to the quarantine tank, you don’t have to monitor and keep your quarantine up with your main aquarium’s temperature and pH levels or vice versa. By the time your fish is ready to be moved back to your main aquarium, its temperature, pH levels, and everything else would have changed already. Hence, it’s impractical to monitor the difference.

Do, however, check that ammonia and nitrite levels are down to zero and that the nitrate is at its acceptable level.

4. Now, you’re ready to quarantine your fish. Transfer your fish and begin medication.

Even though some people would tell you that you should cycle your filter and your quarantine tank before you transfer your fish, the fact is, medications will kill the beneficial bacteria and will therefore make cycling useless.

If, however, you’re going to be transferring newly acquired fish and quarantining it before putting it in your main tank, then, by all means, cycle your quarantine tank.

Test the water parameters daily and perform regular water changes in your quarantine. Wait two more weeks after you’re fish got better before you put it back in your main aquarium. During this time, it is also advisable to begin acclimatizing the fish to the water in your main tank so that by the time the fish is completely healed and ready to join the others, the transfer won’t be stressful.


(Transferring healed fish back to the main tank)

Acclimatizing Fish
Acclimatizing Fish

The popular way is by slowly mixing the water in the main tank with your quarantine tank. Do this by using a drip tube with a regulator for drips. The quarantine tank needs to be placed lower than the main tank to ensure the water from the central aquarium transfers to the quarantine and not the other way around. Set the regulator to drip water every second and remove some water when the tank gets full.


Assuming you used the same water from the main saltwater tank in your quarantine tank, water changes will only be your problem. Be sure that the water you plan to add when changing water is aged (let the saltwater mix sit for at least 48 hours) before putting it in the quarantine tank. Putting your sick fish in a newly mixed saltwater will only stress further your already stressed fish. Besides, you won’t get an accurate reading with freshly mixed saltwater, and it’s critical to monitor the water quality of your quarantine tank all the time.