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In this article, you’ll learn how to set up a quarantine tank and why they are essential.

Here’s what you’ll learn;

  • What is a quarantine tank?
  • Why you need one
  • How to set one up and the equipment you’ll need
  • A few more helpful tips

Let’s begin

What Is A Quarantine Tank?

A Quarantine is a tank or container that is used to isolate fish that are either sick (or infected), or there is a chance that it might be sick. The latter is the most common reason behind establishing a quarantine tank at home.

A quarantine tank is a very common and usual piece of equipment that most aquarists have (and almost every aquarist should have).

Whenever you purchase or procure a new fish, run with the assumption that it might be sick or infected. If not that, it might carry parasites that, even if they haven’t affected that particular fish, can infect others if it’s introduced in the tank. It’s not usually the case, but it’s best to be safe than sorry. So if you are assuming the fish is sick, what do you do with it?

That’s where the quarantine tank comes it. It helps you isolate and observe new fish. Since it will be in a separate quarantine tank (which is relatively bare and open by design), you will be able to closely monitor it, observe its behavior, and treat it if necessary. That’s the second most important function of a quarantine tank: It allows you to medicate sick fish without subjecting all the other fish to the unnecessary and possibly dangerous medicine by putting it in the main display tank.

To summarize, a quarantine tank allows you to isolate one (or a few) fish from others, so you can observe and medicate it (if needed). It can either be used for new fish or existing fish that show any symptoms or signs of sickness.

Further Reading: If you’re sick of reading the old complicated beginner guides then check out our guide: Best Freshwater Aquarium Setup. Check it out!

Why Is A Quarantine Tank Necessary?

There are various reasons why a quarantine tank is necessary. And if you understand those benefits, you will realize that a quarantine tank’s scope goes way beyond a simple “new entry isolation ward.”

  • Acclimate New Fish: When you bring a new fish from a store (even if you are sure it’s free of disease), putting it in a quarantine tank is the smart thing to do. Understand that it has just been removed from the water conditions, lighting, and surroundings that it had adapted to. Getting comfortable in the new surroundings and with different parameters might go more smoothly if it’s on its own. It can learn to eat whatever feed you are providing it, without older inhabitants scrambling around. Also, the stress of being removed from its original place can make a fish sick, which would be far easier to treat in a quarantine tank than in the main display where the fish might be even more depressed.
  • As A Hospital Tank To Use Medications & Treat Sick Fish: That’s equally helpful for new and old fish. If a fish is sick, you can place it in a quarantine tank and treat just that fish. Also, it won’t be able to make other fish around it sick. You won’t have to medicate the water in the display tank (which will impact the health of all the other fish there), so you can tweak the potency of medication to your liking. Similarly, in a tank with so little biomass (one or two sick fish), parameters are relatively easier to control, imperative for fish’s health.
  • Monitor Potential Issues: It’s a bit difficult to observe one fish in the main tank, especially when it’s teeming with activity. So if you think that a few of your main tank fish are showing symptoms of sickness, or they seem off, you can relocate them to monitor for potential issues. In quarantine, it would be easier to observe them. You can figure out the cause behind the stray from ordinary, i.e., water parameters, bullying behavior of other fish, not enough space to swim, etc.
  • Stress & Injury: The existing members can often bully new members of the aquarium. It might merely be that the species don’t get along (like fin nippers with Betta), or territorial disputes among boisterous fish in the main tank. This either results in stress or injury. Stress will manifest in the bullied fish, not eating, not swimming enough, always hiding, losing color, etc. Injuries will be more visible (nipped fins, missing scales). In either case, the best course of action is to remove the abused fish to the quarantine tank, focus on their healing, and then think about a potential solution. In some cases, you can also banish the offending fish to the quarantine, as you work on the alternate aquarium for them.
  • Disease: A broad spectrum of fish diseases can be transferred to another fish. Whether it’s a new addition to the aquarium, or one of the sensitive members of the main tank becoming disease-ridden for any reason, remove them to the quarantine tank as soon as possible. Make sure that observe the symptoms as closely as possible and do your research as to what the cause of the disease can be. If it’s merely something caused by incorrect parameters, the relocation to a quarantine tank might be enough to heal the fish. You can then do water changes in the main tank to ensure proper parameters.
  • Parasites: Quarantine tanks are usually kept bare-bottom (without a substrate) for a reason. Some parasites, which need substrate to stay alive in their “free-living phase,” cannot exist in a quarantine tank. Similarly, an empty quarantine tank (without any host) will be less likely to contain a parasite than the main tank, full of fish and substrate. It will be significantly easier to treat a parasite ridden fish in a quarantine tank than the primary display aquarium. And you will simultaneously be reducing the chances of the parasites latching on to other available hosts.
  • Bacterial Infections: Bacterial infections are a bit trickier to treat. If you don’t know exactly which infection your fish are suffering from, you can do more harm then good. Also, some bacterial medication (especially if mixed in the water) can kill beneficial bacteria and disturb the nitrogen cycle, resulting in more sickness or death. And if you soak the feed in the medicine before putting it in the tank, the healthy fish might eat it, leaving none for the sick one. This problem can be quickly resolved inside a quarantine tank.

How To Set Up A Quarantine Tank & The Equipment Needed

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The first thing you will need is a tank, and that’s where aquarists are a bit divided. Some believe that you should have a proper glass/acrylic tank. The size depends upon the fish size you want to keep. Usually, a 10/20 gallon works fine. Other aquarists believe that it makes more sense to establish a quarantine tank in plastic containers since aesthetics aren’t an issue with quarantine tanks like in a display aquarium. And plastic tanks can be cleaned and re-purposed more efficiently.

A quarantine tank is, by necessity, a bit barer than the main display tank. It needs the essentials, like a filter, heater, thermostat, decorations for fish to hide, etc. And there are also things that you shouldn’t use when setting up a quarantine tank.

A substrate (especially sand), for example, because it can soak up the medication you put in and can be a breeding ground for bacteria or parasites. It would be best if you also didn’t put live rocks in the tank. And most importantly, since quarantine tanks are used for medication, you can’t use filters that process and get rid of medicine before it has time to take effect. So activated carbon is out.

On the other hand, you will need to keep such media handy to use when you need to soak up the medicine from the quarantine tank. For copper-based fish medicine, you might need a special filter to soak up the medicine.

Some of the necessary supplies you will need to set up a quarantine aquarium are:

  • Established Tank Water From Main Aquarium: Water from an existing tank will help start a nitrogen cycle in the quarantine tank. Understand that water itself doesn’t hold many beneficial bacteria (it’s attached to the substrate, aquarium surfaces, and filter media). However, it still helps in cutting down the time it needs to cycle the tank properly.
  • Sponge Filter Media: Unlike water from the display aquarium, sponge filter is a great way to seed quarantine tanks or any other new tanks with beneficial bacteria. Also, since the quarantine tank won’t have to deal with a high bioload, a small internal sponge filter might do just fine. It should be powerful enough to keep the water quality pristine, so you don’t stress out the already sick fish even more.
  • Heater & Thermometer: The heater should be simple and functional. A simple heater with three to five watts per gallon should be sufficient. Remember that bioload doesn’t make a lot of difference to the heater. Its calculation is done based on the amount of water. It would be best if you had something that can keep your quarantine tank warm enough to accommodate fish of your display aquarium, and do it fast. Place a thermometer (as far from the heater as possible) in the tank. You will need to keep a close eye on parameters to ensure the recovery of your fish.
  • No Substrate: But to keep the fish a bit more comfortable, you can try placing the quarantine aquarium on a dark surface (or place a dark cloth/sheet), because a pristine white bottom might stress out the fish.
  • Aquarium Light: Your quarantine aquarium may work fine without light, but if your main aquarium is on a specific light cycle, you can use simple LED strips to mimic that. However, you may have to keep the light off if your fish seem more comfortable in the dark.
  • Decorations: A quarantined fish must have something to hide in. Many aquarists love PVC pipes of varying diameters. You can also go with plastic plants.

Apart from water from the main aquarium, you can also use bacteria start kits. You will also need to have testing kits to check the parameters of a quarantine tank periodically.

Does A Quarantine Tank Need To Be Cycled?

Yes. A quarantine fish tank needs to be cycled just like your main display aquarium. Part of setting up a quarantine tank is properly cycling it to ensure enough beneficial bacteria present to process the waste your quarantined fish produces. When you establish a quarantine tank for a new fish, using media from an already cycled tank and some water is the best way to kick start the process.

If you use antibacterial medication to treat a fish in the quarantine tank, it might kill some of the beneficial bacteria as well. You will need to keep a close eye on your water parameters and watch out for ammonia spikes.

You may not need to keep your quarantine tank running 24/7 just as a backup. But you need to be familiar with the process of instantly cycling the tank, so it can be ready to use whenever you need it.

How To Quarantine Fish?

If you need to quarantine new fish, you can place them in the quarantine tank when you get back from the store. You will need to observe for behavior, signs of sickness, and ensure good water quality in the aquarium. Feed them as usual, and monitor their eating patterns as well. If there are multiple fish, make a note of which ones are aggressive and more docile.

If you remove a sick member from your established aquarium to the quarantine, you need to remove them using a fishnet. If you know exactly what is wrong with the fish, you can start treating them immediately. Stress in the original tank (because of parameters and other members) might be the cause of sickness in your fish. In that case, simply removing them to the quarantine might be enough to cure them.

How Long Do You Need To Quarantine Fish For?

Most aquarists believe that you need to make sure to keep new fish for at least four to six weeks. In some cases, it can be stretched to eight weeks, but four weeks is a minimum. If the fish is sick, you may need to keep it in the quarantine for 12 weeks even. You need enough time to observe and treat the fish (if required), and to get the fish comfortable.

Best Quarantine Tank Kit?

While you can use any old 20 gallon kit for a quarantine tank, or a specially purposed acclimation tank, the best gear is what you put together. You need a sizable tank/container, a sponge filter, some PVC pipe, and maybe a few general-purpose medicines.

What Do You Do With A Quarantine Tank When Not In Use?

Quarantine tanks are not running tanks when they are not in use. They are typically washed and clean until they are needed again, so you don’t have to do any water changes or make sure that parameters are perfect. But you can re-purpose a quarantine tank to:

  • Grow plants: You can use your quarantine aquarium to grow plants. But that would require using a substrate. And since it soaks up medication (especially copper-based), you will need to check copper levels when you are quarantining fish in your now-planted tank.
  • Raise Fish Fry: The quarantine aquarium can act as a fry nursery. Keeping them in a community tank is usually not a good idea, so you can remove them to a separate quarantine aquarium until they grow up to a decent size. Ensure you keep up with adequate water changes in the quarantine aquarium when it’s holding fish fry.

Watch This Video On How to Make a Quick & Easy Quarantine Tank