How To Quarantine New Goldfish

It doesn’t matter if your new fish came from your best friend’s personal aquarium; quarantine is always necessary. Think of it this way… you have invested untold hundreds of hours caring for your fish and maintaining their health. You have possibly even invested hundreds of dollars on the cost of your fish themselves. Any time you add a new fish to your established collection of fish, you are adding a new set of microbes (and possibly, pathogens) that come along with that fish. It is not worth risking your entire collection of fish simply to avoid the hassle of quarantining a new fish. No quarantine procedure is 100% foolproof, unless it is a lifelong quarantine, which is not usually reasonable. There are some fish health issues that will not become apparent during any length of quarantine. But by quarantining your new fish for 4 weeks, you will drastically reduce the chance that your new fish will infect your entire collection of fish with a potentially deadly pathogen.

Why You Should Quarantine New Fish

Reason 1
There are a lot of dishonest companies out there. They will tell you whatever it takes to make you feel that their fish are perfectly healthy, even while knowing full well that their fish are currently being plagued with gill flukes or columnaris. Most businesses are not about being ethical and doing the right thing; they are about making a profit. Do not make the mistake of trusting the word of a salesperson when it comes to the health of your entire collection of fish.

Reason 2
Even if your new fish is 100% healthy, which it may well be, moving from the seller’s environment to yours is a big change and is likely to cause some degree of stress. When fish are stressed, they are more susceptible to opportunistic pathogens. Opportunistic pathogens are those that are always present in small numbers, but under normal circumstances the fish’s immune system is capable of fighting those pathogens off. Under stress, the same fish may be unable to adequately fight off these opportunistic pathogens and may become sick. Quarantining your new fish in a healthy environment allows it to recover from the change it has experienced and allows you to keep a close watch on it to ensure everything is going smoothly. Your fish may seem fine when it first arrives, but remember that many issues from transport can take 2 weeks to become apparent.

Reason 3
Fish from isolated environments may have developed immunity to a certain set of microbes that could be different from the set of microbes that your fish have immunity to. When you bring in a new fish with a new set of microbes, your fish may become sick. The same is also true in reverse. Proper quarantine of new fish, especially when the last week of quarantine involves gradually mixing water from the main tank to the quarantine tank and back again to more slowly acclimate the fish to each other’s microbes, can help combat this problem.

Reason 4
Simply put, your new fish might be sick. They could be harboring something as easily-treated as gill flukes, or something as nefarious as SVC (Spring Viremia of Carp) which is 100% fatal with no treatment. People have lost entire collections of koi and goldfish worth tens of thousands of dollars to SVC. Even if the new fish carries with it something as easily-treated as gill flukes, the cost of the praziquantel will be much cheaper to treat the small volume of your quarantine tank than it would be to treat your entire collection of fish.

Guide to Proper Quarantine Procedures

A good quarantine procedure has three equally-important components: A) the quarantine tank setup, B) maintenance of the tank, and C) medications. All three components work together for a successful quarantine.

The Quarantine Tank
The quarantine tank should provide at least 10 gallons of space per fish. Sufficient space is always important for goldfish, but it becomes especially important during quarantine. If there is an issue with your new fish, even a very minor one, insufficient space will make the problem much worse. Accumulated toxins from waste products will put compounded stress on the fish, making them less able to fight pathogens. The tank does not need to be a traditional glass aquarium, but it should be a container with clear sides to provide a good view of the fish, as it can be difficult to observe signs of disease without a clear side view of the fish.
The next consideration is filtration. It’s very important to have at least 10x filtration for sufficient water flow through the filter media. This means that for a 10 gallon tank, you’ll need a filter with a flow rate of at least 100 gallons/hour. There are many great filters to choose from, including the Aquaclear filters, which provide a lot of space for filter media and are highly customizable. The filter should have a bottom layer of sponge and be filled to the top with biological media (ceramic beads and rings, bioballs, etc.).  All of this biological media should be taken from a healthy and well-established (cycled) tank of yours. Ideally you should add the cycled media to the QT filter immediately before adding your new fish to the QT tank. This way the beneficial bacteria living on the filter media won’t starve by being placed into a tank with no fish for a few days while you wait for your new fish to arrive. It is advisable to add an air stone and a thermometer to the quarantine tank as well.

Diligent tank maintenance is especially important during quarantine. Even though the filter is full of biological media that should be full of beneficial bacteria, it is still good practice to test the water daily for at least the first week of quarantine. You’ll be testing for ammonia, nitrite, nitrate, pH, and checking the temperature. A good general-use test kit to use is the Freshwater Master Test Kit by API; it contains all the tests you’ll need at a reasonable price. Ammonia and nitrite should always be zero, while nitrate should be less than 10. The pH should be stable, and somewhere between 7.2 and 8.4 (goldfish tolerate a wide range of pH, as long as it remains stable). If at any time ammonia or nitrites register, a water change should be done immediately. Your test kit and Python water changer will become your best friends during the quarantine process. Remember, any equipment that you use for the quarantine tank should not be used in your main tank(s), so as to avoid cross-contamination. To make water changes during quarantine easier on you, you will want to have a dedicated quarantine Python water changer that you do not use on any of your other tanks.

It’s a great idea to do a near 100% water change for the QT tank every day for the first week. Your new fish is susceptible to pathogens during this time, and fresh clean water is the best prevention against many goldfish problems. After the first week, water changes can be gradually scaled back as long as the water parameters remain at acceptable levels. Use Seachem Prime or Amquel Plus to remove chlorine and chloramines. These products also provide some temporary protection in case of a sudden ammonia or nitrite spike.

Hopefully you had the benefit of seeing your fish (either in photos or in person) before it arrived so you could be sure to pick a fish that appears healthy. But even an apparently healthy fish could have issues that may eventually be transferred to your main tank. In most cases, it should be assumed that all new goldfish have some type of parasite, and they should be treated accordingly.

The most common treatment used on new goldfish arrivals is salt because it can kill an assortment of external parasites. It must be pure salt with no additives. You can either use Aquarium Salt from the pet store, Morton Canning & Pickling salt, or any type of water softener salt that contains no additives. The salt concentration must be brought up to .3%, which is typically 3 level teaspoons per 1 gallon of water, depending upon the grain size of your salt. In the case of Morton Canning & Pickling salt, for example, .1% salt will actually be 3/4 teaspoon per gallon because of the large grain size. It is best to bring the salt concentration up slowly to avoid shocking the fish. First add 1 teaspoon per gallon. 12 hours later, add another 1 teaspoon per gallon. Then after another 12 hours, add another 1 teaspoon per gallon of water. At this point the salt concentration will be at .3%. The salt should be dissolved in a bucket of tank water before adding it to the tank. Keep in mind that with each water change, you’ll need to add back the amount of salt you took out. For example; if you change 75% of the water, you will need to add back in 75% of the salt that was in the tank before the water change. A salt concentration of .3% should be maintained for about three weeks to be sure any possible parasites are eradicated.

Prazi is the other medication typically used in quarantine, and this treatment kills gill and skin flukes.  Flukes are so common in goldfish that all new fish should be treated as if they have flukes. Prazi is a relatively “safe” medication to use as it is difficult to overdose. The most common type of prazi used by goldfish keepers is a liquid form, called PraziPro. The prazi treatment must be done in several repeated doses, because it only kills adult flukes, without harming the fluke eggs. The fluke eggs will not hatch with prazi present in the water, so each dose must have a couple days in-between with no prazi in the water to allow the fluke eggs to hatch. I prefer to keep prazi in the water for 3 days, followed by 2 days with no prazi, and repeat this cycle 4 to 5 times. The prazi treatment can be done at the same time as the salt treatment.  

Some people choose to wait a few days before beginning any treatments. This may be a good idea, because it gives the fish a chance to settle in and gives you a chance to observe the fish’s behavior before jumping right into treatments. Regardless of when you decide to begin treatments, carefully observe your new fish for the duration of quarantine to detect potential problems early on.

Microbe Acclimation
If you seeded your quarantine tank with biological filter media from your main tank, you will have already shared some of your fish’s microbes with the new fish and thus helped your new to become accustomed to these microbes. As an extra precaution, you may choose to extend quarantine for one additional week so that you can slowly begin sharing water or filter media from the quarantine tank with your main tank. This will allow your main collection of fish to more gradually adjust to the microbes living on your new fish.  

Enjoy your new fish! If you follow the steps for proper quarantine, it’s very likely that you will enjoy a healthy and happy new fish that will integrate seamlessly with your other fish.