How Long To Quarantine Fish

Quarantine is a crucial part of fishkeeping that is often overlooked by the more inexperienced hobbyists.

There are many advantages to having a quarantine tank in your collection that will benefit your aquarium in the long run. 

How long to quarantine fish

However, those who don’t know how to quarantine properly or who just may not know a lot about it will question how best to quarantine their fish.

Or perhaps you’re already convinced about the merits of the activity but don’t know how long to quarantine fish for?

How long to quarantine fish

Advice varies from 2 weeks to up to a year depending on the fish and tank environment, but a quarantine period of 4 weeks is best.

This is because various diseases and bacteria have different life cycles - especially depending on the temperature in your aquarium tank - but a period of at least 4 weeks should get rid of any unwanted illness or parasites.

Or at least allow them to display themselves so you can treat your new fish before adding it to your main tank.

While that may seem like a long time to wait, patience is key in ensuring the health of your already existing fish.

If you introduce new fish to your main tank too early, it could end up costing you more money in the long run.

Instead of having to treat one fish in its own tank should any parasites or diseases become apparent, you will have to treat every fish that you have in your main tank.

Having a quarantine period of at least a month will allow your fish to display any symptoms of unwanted parasites or bacteria.

It will also give them a chance to recuperate from the move and build up their immune system.

Being transferred and transported can cause fish stress, which in turn has an adverse effect on their immune system and makes them more susceptible to anything they may have come into contact with. 

It’s also worth bearing in mind that there might be certain pathogens in your main tank which your already existing fish will be used to.

A newer fish that is stressed won’t have the adequate immune system needed to defend itself against these pathogens.

Once the time period of at least a month has passed and your new fish shows no signs of disease or unwanted parasites, they will be fine to add to your main tank.

Benefits of quarantining fish

There are numerous benefits to properly quarantining your fish before you add them to your main tank.

If you’re tempted to skip the quarantine period, it’s important to bear in mind that this is to protect both your new and already existing fish.

Some of the benefits of quarantining your new fish include:

  • You can minimize the risk of introducing the potential spread of unwanted diseases and parasites
  • You can easily condition your new fish to the water parameters of your main tank
  • It allows your new fish to acclimate after their stressful traveling period
  • The tank itself can also double as a breeding tank, a “grow out” tank for young fry, a recovery tank for harassed fish, or a treatment tank for infected fish

While your new fish may appear healthy, they may also be harboring parasites that are yet to go through their whole life cycle.

For some parasites, the final stage of their life cycle is when you can actually see them, by which point it’s too late if you’ve already added this new fish into your main tank.

A quarantine tank will also allow your new fish to build up their immune system.

A stressed fish is more susceptible to anything that might be in your main tank.

If your main tank does have any pathogens in it, your already existing marine life has likely built up an immunity to these. 

A newer, more stressed fish won’t have this advantage, as their immune system will be compromised due to the trauma of being moved.

It will be worth trying to mimic the environment of your main aquarium in this quarantine tank to acclimate your new fish.

You should try and keep the water at a slightly higher temperature, too, as this will help to speed up the life cycle of any potential parasites that may be present and allow you to deal with them accordingly.

Optimal quarantine tank environment

The ideal quarantine tank environment will depend upon several factors.

One of these includes the size of the fish that you are hoping to introduce to your main tank.

The larger your chosen fish, the larger tank it will need. 

It’s important to keep all equipment that you use for this quarantine tank separate from the equipment you use for your main tank.

That includes any nets or siphons that you use regularly in your quarantine tank.

You will need to ensure that everything you use in this tank has been properly sterilized.

We’d advise against adding substrate to the bottom of your tank.

That’s because this will make it harder to clean, especially if you’re having to sterilize everything you use in the tank.

A bare bottom tank will be easier to clean, and will also be much easier to sterilize after use.

You should also avoid adding porous stuff like lava rocks to the quarantine tank because the pores can harbor any unwanted pathogens.

You should try and mimic the same water parameters as the main tank that you want to add your new fish to after the quarantine period is over.

You can keep the temperature slightly higher if you wish, as not only will this help speed up the life cycle of unwanted parasites, it can also help to boost your new fish’s immune system. 

Try and opt for low lighting in the quarantine tank if you can, as this will be much more welcoming to any stressed fish.

It will be worth adding some hiding places or shelter for the new fish, too.  PVC elbows are a popular choice because they're cheap and easy to clean.

Not only will this minimize any stress they could experience, but it will also give them comfort. 

It’s also worth remembering that your quarantine tank will still need a matured filter. You will need to carry out weekly water changes, too.

Some hobbyists also like to use preemptive treatment or medication in a quarantine tank in an attempt to get a head start on any problems that might occur.

While there is nothing wrong with this if treatment is administered correctly, it can cause your new fish more stress.

It’s worth remembering that treating for any diseases the new fish might not actually suffer from could lead to medication-resistant pathogens which will pose a problem in the long run.

Final word on quarantine

Quarantine is essential for maintaining healthy fish and a healthy marine environment.

If it’s not done properly, this could have a detrimental impact on your main tank and cost you more money in the long run.

While it may be tempting to skimp on the length of time you quarantine your new fish for, you should try and stick to a period of at least 4 weeks for the best results.