Why Should You Quarantine Your Fish?

UPDATED, based on new research (2023) Quarantining in general is practiced in many situations by many institutions, such as zoos & public aquariums, and customs control for the importing of animals, in order to prevent the spread of disease to an existing environment. Diseases aren’t always apparent, and time may be needed to conduct tests or to monitor a new animal to diagnose any possible diseases it may be harboring. Professional quarantine procedures are essential to prevent the spread of disease. Just think about how quarantining works with people, now in 2023 – separating the sick from the non-sick is the only way to ensure for sure that those who are not sick do not catch disease. It may be unpleasant and annoying to quarantine fish, but you will be rewarded with healthy and happy fish looking great in your display tank for years to come! If you take reefing and fish-keeping seriously, quarantining your fish, invertebrates and other animals should be a must whenever you purchase or obtain new critters for your aquarium. You want to make sure your new fish are healthy before adding them to your display tank – you wouldn’t want to make any new fish sick. The other benefit is that sick fish can only be treated in a quarantine tank as the medications and techniques used may distress or kill other fish, shrimps, corals and even beneficial bacteria in the filter. When quarantining, there are two main techniques – the quarantine and observe method, and the quarantine & medicate method. Both of these techniques have different supporters, but we feel that the “quarantine and medicate” method of quarantining saves quite a bit more time. Quarantining and observing fish without medicating them will put less stress on healthy (disease-free) fish however, and so long as they pass the quarantine period with no symptoms, they can be considered ‘disease free’. However, in my experience, about 8 in 10 fish bought at home will develop some sort of disease. This rate highly depends on the source of your fish (what kind of practices your shop uses) and the species. In the interest of saving time and having peace of mind, we treat all new fish to a medication regimen – regardless if they are showing symptoms or not. It is true that this can place unnecessary stress on a fish, however, most fish survive the medication and you will have peace of mind knowing your fish is for certain, parasite and disease free. A proper quarantine regimen will ensure that you protect your existing investment of fish in your display tank from diseases and parasites – which are highly contagious and often kill fish swiftly. Quarantining will also protect yourself from heartache and frustration, albeit at the expense of a little patience 😉
A sick fish with a severe case of Saltwater Ich, also known as Marine White Spot Disease. Caused by the parasite Cryptocaryon irritans. This disease can be prevented by quarantine. 
Quarantine is important as fish or inverts purchased in fish or pet stores are not in their natural habitat; they are crammed into small confined tanks with dozens or in some cases, hundreds of other fish – all sharing the same water supply. It takes only one sick fish a few days to infect many other fish – so it is wise to consider all new fish from stores to be exposed to disease, and therefore, sick. All sick fish should be quarantined for observation and treated before addition into your main display tank.
A overstocked fish store – The perfect breeding ground for marine fish diseases & disease transmission
Quarantine tanks also allow you to acclimatise an animal in a more controlled setting, as there is less water in the tank, meaning you can more precisely control the dosing of medications. On top of that, a quarantine tank also allows you to acclimatize new tank additions without the disturbance of other tank mates to encourage feeding. A fish must eat as soon as possible after leaving the fish store in order to survive. A healthy fish is a hungry fish! Additionally, quarantine tanks also function as treatment tanks for taking care of fish or inverts when they become sick. This is important, as most treatments for marine fish diseases affect water quality, and in some cases are even toxic to other animals such as inverts or corals, making treatment of a fish in a display tank impractical.
Cupramine, a popular copper based medicine, is essential when quarantining new fish, but is toxic to inverts.
Starting a new salt water tank? If you are setting up a new tank with just corals, live rock and sand means you can skip medication treatments in most circumstances and leave the tank fallow as most fish diseases cannot survive without fish for more than eight weeks. After 8 weeks, all fish parasites and diseases usually cannot continue their life cycle as there is no host. After this period, it is more than likely safe to add quarantined fish to your new tank. If you have a new tank and you have also purchased fish, do not quarantine your fish in your main display tank, as residues from medicines, even in minute amounts, can be harmful to corals and inverts. This is extremely important when treating fish with copper based medications. Quarantine or treatment tanks must always be in an independent tank, used only to treat sick fish or to quarantine new fish. Note that because inverts are sensitive to copper medications, inverts should be quarantined separately from fish, in their own quarantine tank setup. If you reuse the same tank for quarantining fish and inverts like shrimps or crabs, there is a chance that any remaining copper medication could prove fatal.
A complete quarantine tank – PVC piping, temperature control, basic filtration & lighting.
Many hobbyists get lucky with their first few fish and setup a new tank without quarantining. The urge to add new additions to your display tank is usually strong – what would be better than to see all your new fish swimming around happily in your new tank. Try to resist this and follow quarantine procedures as if you don’t you will play a fool’s game of Russian roulette; each new fish added is potentially a carrier of deadly disease and could wipe out an entire tank. Save yourself money & heartache. Make quarantining a habit, and reef-keeping will be a much more pleasurable hobby!

Next: How to set up a Quarantine Tank >>