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Quarantine Aquarium Fish: What You Need To Know

Quarantine Aquarium Fish: What You Need To Know 1

When should you quarantine in your tank? What procedures should you take? If you have asked either of these questions, then this article will be the one you want to read. Quarantining your fish can be very important to avoid many problems that could occur. This process could be the difference between life and death in your fish. It is up to us, the fish keeper to do everything we can to save them.

I will guide you in how to properly quarantine your fish. I would say that keeping a quarantine tank and actually using it was one of the most pivotal things I have done for my fish. Some fish will need to be quarantined more so than others. It isn’t always for the new fish that you are quarantining, but also for the fish that are already in your tank. They can be sensitive to any disease that the new fish is introducing. Your new fish may be infected with something and you would not even know it.

There may be many reasons why you would quarantine your fish. Of course, the most important reason is to try and save your fish. If you do not quarantine then it can become an expensive waste of money to lose your fish. This could be anywhere from the $5 fish you are introducing, to thousands of dollars in wasted fish that are affected by just being exposed. You could lose everything if you are not cautious

Freshwater and saltwater quarantining really serve the same purpose. There will be different things you need to focus on though. With freshwater, you will have to worry about introducing plants, rocks, wood into your tank.

Saltwater aquarium quarantining isn’t any different. Quarantining marine fish is basically the same concept as freshwater. It may be more important though due to the contaminants that could come with the new fish. If they are wild caught, which most marine fish are, then they could bring a disease from the ocean. These diseases can quickly spread and kill off your fish. You have more things to deal with when it comes to wild fish than farm grown.

You can only trust your own quarantine process. While it is best to start with a clean fish specimen, that isn’t always the option. You may order the fish and never see what state they are in before they arrive to your door. If you notice anything ‘fishy’ going on in your aquarium, then you shouldn’t put the new ‘possibly diseased’ fish into your display tank.

Note: Some fish are sold as ‘pre-quarantined’. Meaning that the seller will quarantine your fish prior to shipping them out. I wouldn’t do this for a few reasons. There is no guarantee that the fish doesn’t carry something that will cause an outbreak in your tank. I also feel this extra stress is completely unnecessary.

While putting your fish into quarantine could be helpful, it could also be harmful. You have to think about the fish and what they will go through. If it is a new fish, think about how much they possibly could have changed tanks in the recent days or weeks. They could have gone through a whole assortment of different fish tank parameters. This may be the exact reason for why you usually lose fish right after introducing them to the tank. Acclimation is possibly one of the most common reasons to have a quarantine aquarium.

For this acclimation, you may want to plan ahead. Planning will be key to getting the tank setup and cycled prior to the arrival of your new fish.



Like I said there can be many reasons to quarantine your fish. It can be the critical step in order to make sure they survive. The reasons why you need to quarantine could be things like diseases, chemicals or even fish behavior.

These are some common reasons to quarantine your fish:

  • Treating Disease – There could be a number of diseases riding on the fish you just purchased at the fish store. You want to be careful when selecting fish that you only purchase fish at appear healthy. If they are diseased at the store or look like they are gasping for air, that should be a red flag for you. Common diseases are things like velvet, skin flukes or Ich.
  • Ich – This is very a common disease associated with stressed-out fish. This disease appears as white spots all over the body, starting around the gills and fins. Ich usually happens with a new aquarium, most likely known as the ‘new tank syndrome’. You can treat Ich with store-bought medications. The best way is to prevent it, to begin with, is by just having a fully cycled tank.
  • Fish Aggression – Sometimes fish can be really aggressive and should be quarantined from the others. You may decide to quarantine the bully fish or the victim depending on the situation and what could work better. Sometimes all you need to do is take the female out of the tank when there are two males fighting each other. They will most likely be best friends in her absence.
  • New Fish – When you get a new fish you should definitely think about quarantining it before adding it to your display aquarium. They could be carrying a variety of diseases. You also want your new fish to be at their best strength when you go to introduce them into your main aquarium.
  • Aquarium Acclimation – This is almost the same as the one above but under a slightly different approach. Your new fish will come from different water parameters than your fish tank. Even if they come from a fish store down the road, your aquatic environment is completely different. Things to watch for would be water hardness, pH, temperatures, nitrites nitrates, and ammonia. This sudden change in water parameters can be very stressful on your fish. You want to take the aquatic acclimation process seriously.
  • Breeding Environment – Say you have a pair of angelfish about to breed. They put their eggs up, and it’s just a matter of time before the other fish start to eat them. You could quarantine the aggressor so that when the eggs hatch the fry will be safe. After the fry hatch, you can quarantine them and bring the other fish back to the bigger tank.
  • Chemicals – Say something happened where some household chemicals got into your aquarium. You have the opportunity to quarantine your fish while you rebalance the contaminated tank and remove the chemicals. This is a tricky one if you do not already have a quarantine tank set up. The extra time needed for cleansing your tank could cause issues if there are too many fish in the population, there will be high stress in smaller spaces. You could be potentially going from a large tank to a smaller quarantine setup and the fish will have to adjust to this smaller area, which will be where that stress is from.
  • Harsh Minerals – Just like the chemicals above, minerals can also be deadly to your fish. Copper, in particular, is very deadly to many crustaceans and some fish. You want to make sure that you know what you are putting into your tank, not all rocks will be a good addition.

Note: Some people use copper in their tanks as a way of killing off disease. I highly recommend against this and I would never use this in my aquariums. Copper medications require that you dose it in high amounts before it is effective. It is just too deadly to be worthwhile in my opinion.


There is no set way that you can quarantine your fish. Many people will have a different way of going about it. Some will make an elaborate setup to fight any problems that come up. You may opt for a simple setup that you can take down and stash after needing them.

I will try to outline three different methods for quarantining your fish:

Tank Transfer Method

There is the method where you have two quarantine tanks, the Tank Transfer Method (TTM). In this process, you will keep the fish in one tank for 3 days and then move them to the other. After you move them, you will sanitize the previous tank and get it set up again so that it is ready to take the fish when you are ready for another swap. You would keep doing this for about two weeks until you think the fish is ready to go back into its normal aquarium. Some state that you can risk having ammonia spikes, which is true of any sudden water changes. I do not see this as a major problem because you are only keeping the fish in a tank for a maximum of 72 hours. This tank to tank method is done without chemicals or medications, you can skip copper altogether. This doesn’t mean that you don’t have to prevent medications. You are welcome to use them, and this setup may allow for easier use and removal afterward. For a complete breakdown of the TTM quarantine method, you should check out this forum post over at While it is focused on saltwater fish, it still can apply to freshwater aquariums.

Quick Dip Method

Another method would be more of a dip and medicine process. You would take your fish and do a freshwater dip for a short duration. This is meant to kill off contaminants in the fish. They sudden parameter change will shock the fish, so do not overdo it. Handling your fish is key, do not mishandle them in order to prevent injury. You may decide to do a second dip in new freshwater but with some store-bought medication. Make sure you read and understand the label, from the instructions to the chemical makeup. I wouldn’t to use a harsh chemical-based medicine and harm my fish. After these two different ‘dipping’ steps you will place your fish in a clean quarantine tank. You would want to keep them in the quarantine tank until you do not notice anything wrong, this could be from 14-30 days most likely.

Copper Medication Method

I saved this one for last. I debated on including it because I do not condone it myself. Copper. There is a method where you use a copper based medicine to clean kill of disease. Some recommend this but I don’t. It would require extensive days to work and could really mess your fish up and even kill them. It wouldn’t work for any scaleless fish such as loaches, no catfish, and definitely not invertebrates. For saltwater, copper will kill off corals, crabs, shrimp, and snails as well. One store bought copper based medicine option is Seachem Cupramine. It will have limited amounts of copper and are also bound on amine, so it isn’t as harmful to your fish. Either way, you want to make sure you are doing a test for copper. You can purchase copper testing kits.

While you are testing for copper you should also get an ammonia test kit as well. Ammonia can spike at any time and they can really kill you fish fast. Ammonia is caused by the breakdown of debris and fish waste in the tank. It can be neutralized by an acid or alkaline, but this doesn’t make it safer for fish either. You can treat this in the above quarantining methods for ammonia by using store-bought options just as Seachem Prime. Dosing Prime will help with the sudden ammonia spikes you could experience. Ammonia can be exacerbated by the increased pH or temperature of the water. Make sure to keep these parameters in check as well.

Tip: The orange Home Depot ‘Homer’ Buckets work great for quarantine tanks. Make sure you rinse them out and do not use them for any other purpose but to quarantine fish. This will help keep it chemical free.


The duration as to how long you should quarantine your fish will vary depending on the method used, the type of disease your fish have, and the severity of the infection. There may be a case where you have to keep a fish permanently quarantined because they have become a pest to their tankmates. If that is the case, I would think about giving them a new home either in a new, more appropriate aquarium or give them to a friend who has a suitable environment.

I would have to say that for diseases you should be able to get rid of most infections within two to three weeks. Copper-based cleanings can take longer, at about 14 to 21 days or even up to 30 days. I feel that this could be excessive stress on your fish and I do not recommend it.

For acclimation purposes, I would also stick closely to the two-week approach. You should know by the end of those 14 days as to if your fish needs further help or not. If they are still showing symptoms then I would keep them there longer. Cycling the water to keep it fresh and disease free. Make sure you are keeping the tank clean past this time period. You shouldn’t have issues like this too often, they are only the exception.


Tank Quarantine Divider – Sometimes you do not need to quarantine your fish because of the water. It isn’t always the water causing issues but instead of from the tank mates not getting along. In this case, you may want to consider an aquarium separator or more specifically a tank divider. This is a mesh that is fed into a rail frame that goes in between sections of your fish tank. The mesh is an aquarium safe polymer material that can be cut to fit your tank. The water flow will not be restricted, and it also allows for even temperature distribution. You can use this for bully fish, new fry, or to keep a breeding couple happy without needing a separate tank.

Separate Quarantine Aquarium – This is the method with a separate fish tank. It is when you must get your fish removed from your main display tank. You could be putting your fish in a new tank to kill off a disease or prevent it from spreading. You may need to get that particularly aggressive fish out of your display tank. What about the new couple that is about to breed? There is also the need to acclimate new fish. So keeping a separate tank could serve so many purposes, and having it will let you fix those problems quickly.

Quarantine Bucket – You do not need to always go with the fanciest option out there. I myself will use a 5-gallon utility bucket that I get cheap from Home Depot, specifically their orange ‘Homer’ bucket. This simple bucket will serve the same purpose as any quarantine tank. Just make sure that it is only used for fish purposes. Do not use the bucket for anything else so that you can minimize the effects of chemicals killing your fish without warning. Also having extra buckets can give you a quick option to get your fish to safety if something were to go wrong.

Fish Medicine – You always want to pick the most appropriate medicine for the type of infection that your fish have. I recommend you stay wary of this type of cleansing. There are reasons to need this but not all situations require it. Some of the copper-based store-bought options are Coppersafe or Cupramine. Remember less is more in all medicine situations, just like humans, fish can be affected by toxic levels of anything.

Hydrogen Peroxide – Sometimes you just need to do a light-detoxifying of your fish. I have often used a small amount of peroxide diluted in water to kill off contaminants. Just a quick dip is all that is required. After the dip put your fish back into quarantine. You may need to repeat these small diluted peroxide dips in order to fully remove all contaminants. So maybe you are just doing a quick removal of disease, or you are doing a precautionary cleaning for a new fish, peroxide can be a solution that causes lesser harm.

Any quarantine tank could need these extras to make a properly operating environment:

  • Quarantine Container – This could be an extra aquarium, or as simple as a bucket. Just as long as it is clean.
  • Water Pump and Filter – The water will need to be cycled to filter out biowaste. This will help cycle your tank.
  • Aquarium Heater – The temperature needs to remain constant no matter what situation your aquarium is in. Temperature swings can stress your fish.
  • Air Pump or Plants – You will need to provide constant oxygen. Oxygen helps blood cells operate. Some quarantine tanks can get by with plant provided oxygen.
  • Lighting – This would only be needed for extended quarantining. If it is a short quarantine then you can go without lights.
  • Substrate (optional) – This serves no purpose and could cause other issues with balancing a new quarantine aquarium. The only argument I could make would be a way to calm the fish in this environment.


Fish are not the only things that should be quarantined. They may seem like the most obvious purpose for quarantining, but other possible things you could include are plants, rocks, and wood.

Plants should be quarantined before putting them in your aquarium. Depending on the source of the plants, there could be a number of different contaminants coming with them. There could be rot that will start the process of decay in your substrate as soon as you put it in there. Always clean the roots of all waste, substrate, and anything else that shouldn’t be there. You can also prevent introducing hitchhiking snails by quarantining your plants ahead of time. If you put these snails in your display aquarium then you will have a hard time getting rid of them afterward.

Rocks just like plants can come with bad hitchhikers. More importantly is the chemical composition makeup of the rocks that you would want to quarantine for. I advised getting a test kit to see if a rock reacts to the acid chemical process. You can easily kill your fish with a badly selected rock and you may not even know the cause of it. Putting rocks in the aquarium water to see if there is a reaction would be the same a quarantining them before placement into your precious aquarium.

Wood has many crevices that could house bad bacteria. There is also the risk of putting too many tannins into your tank. I always put wood into the water for quarantine first. This will cause it to soak in the water, for the hopes that it will not float when put in my aquarium. It will also allow the tannins, the dark part of the wood, to seep out and get flushed with a water change. If you leave the tannins in the wood, it can dirty your water and hurt your fish in higher amounts.

Check out this video from The King of DIY on YouTube, this video goes over how to add new fish to your aquarium. This is for a new tank setup, but some of the same ideas can apply to an already established tank.


Importance of quarantining should be at the top of the list for all aquarist. There are so many benefits to keeping a quarantine tank. You are the one person that is in control of your fishes lives. If you see a problem you might want to consider quarantining them.

Make sure your quarantine tank is cycled. A rushed quarantine aquarium can be almost as deadly as just leaving your fish to fight it out themselves. New tank syndrome usually spells out devastation for all of your fish. Ammonia can spike and will kill anything without warning. You want to setup and monitor the aquarium you configure for quarantine purposes.

The process of quarantining fish can be very stressful on fish. Just think about it, you wouldn’t like to be yanked out of your home, especially when you are not feeling well. This can be particularly the case for new fish. You get the fish from the store and they are already stressed, then they have to adjust again to your tanks parameters. These frequent changes can be the main reason you can lose fish right after adding them to your aquarium.

I hope that I expressed why you would quarantine aquarium fish. Maybe you needed a few questions answered, and you are now more prepared to tackle the problems plaguing your fish. Remember taking care of them is ultimately up to us, the fish keeper. Cleanliness is next to godliness, do not put contaminants into your display tank that will give you tons of issues.

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