How Long Do I Need to Quarantine my Marine Fish?

(Updated 2023) Now that you have your quarantine tank set up, and armed with a range of fish medication, you might wonder how long do you need to quarantine your marine fish?

We have devised a quick and sensible quarantine method below, but the full answer is, as with many things in this hobby, “it depends”. It depends on your tolerance for risk and on your patience. It also depends on what kind of fish medications you choose to use, and for how long. 

Sensible quarantine durations for marine fish generally range between 21 and 76 days (note this is 76 days back-to-back where your fish are not showing any symptoms or sickness). If your fish are showing symptoms, you must treat that disease and then restart the quarantine period once they are recovered.

The duration of the 76-day quarantine period became convention based on a study that indicates marine Ich, aka Cryptocaryon irritans, one of the most prevalent diseases in fish, would have to appear in any quarantined fish during this long quarantine period. If the disease doesn’t show up within 76 days of being introduced to a quarantine tank, it is safe to assume that the fish don’t have Ich. 

The problem with this quarantine method is that it may be overkill – the study of  Cryptocaryon irritans that this method is based on states that it takes 76 days to be sure a fish is free from Ich. What it also states is that this duration only happens when the tank water temperature is low (the temperature in the study was 68 F or 20 C). New studies now show that by increasing the temperature of your quarantine tank, you can safely reduce the quarantine period. This is because, at higher temperatures, Marine Ich (as well as several other kinds of parasites and infections) have a sped-up lifecycle – meaning that if you run a quarantine tank at a higher temperature, any diseased fish will show signs of disease much earlier on in the quarantine period. 

Based on this new information, many aquarists and reef keepers have found that a 6-week (around 42 days) quarantine duration with warm (78-84F or 25-28C) tank water conditions will force most diseases to appear in your quarantined fish during this period. We have had great success with running our quarantine tank at 82F / 27C. Check out our super easy guide on how to set up a quarantine tank and what equipment you would need if you haven’t setup your tank already. 

[How to Quarantine Marine Fish Video]

Now we know that a 6-week quarantine period of marine fish is generally accepted as safe, how do we take care of the fish and dose medications during this time? 

Lucky for you, below is the method we use to quarantine our new reef fish tank mates. We treat our fish prophylactically (which just means we pre-treat our fish before diseases even appear) once they start eating after being introduced to the quarantine tank. This pre-treating allows for the shortest duration of marine fish quarantine.

ReefDIY’s Easy Marine Fish Quarantine Method

Hint #1: remember to use old tank water in your quarantine tank – this has the benefit of saving you on making new water for your tank and helps maintain the consistency of the water parameters in your quarantine tank. Clean the filter media in water that you throw away during your water change. 

Hint #2: remember a fish that eats is a fish that lives – you must get your new fish eating as quickly as possible. We always buy live Mysis shrimp (you can hatch your own with a soda bottle) to feed our new marine fish as they start their time in their quarantine tank. Feed your fish multiple times a day if possible, and manually remove their waste as it appears.

Hint #3: Use Seachem’s Prime on days when you are not using cupramine to help remove any ammonia buildup. You cannot use this cheat however when you are dosing Cupramine as the two chemicals will interact and may kill your fish.  

Hint #4: If your fish show any symptoms during the quarantine period try to determine what disease your fish has and treat for that disease specifically. Generally, you should not mix medications as the effects can be unpredictable, meaning you should do a water change before adding any new medication. Return to the quarantine method below if your fish is behaving normally and eating. 

Hint #5: The table below works with most fish, but not with lionfish, eels, pufferfish, mandarins or pipefish as these fish do not tolerate copper. ‘

Treatment DayDisease TreatedMedications in WaterNotes
Day 0-1NoneNone

Ensure that the quarantine tank is set up properly and seeded with a filter sponge from an existing tank.

Drip acclimatize your fish with dim lights. Attempt to feed fish with live mysis shrimp. 

Dose small amount of Seachem Prime at the end of the day.

Day 2-3NoneNone

Continue feeding fish. Observe fish to see if you can see any symptoms. Remove any fish waste as quickly as you can. 

Dose Paraguard – 5 mL (1 capful) of ParaGuard for every 40 L (10 US gallons), per day as long as fish continue to eat. 

Dose small amount of Seachem Prime at the end of the day.

Perform full water change (100%) at end of day 3, before Day 4. 

Day 4Parasites, IchCupramineBegin dosing Cupramine according to instructions (20 drops per 40 L), with tank of new water from display tank.  Remember, do not use with inverts. Test copper concentration to 0.25 mg/l (use a Salifert Copper test) – this is the beginning concentration for Cupramine. Do not exceed this concentration. Test copper daily. Make sure you read the FAQ’s for Cupramine as it may interfere with ammonia tests.
Day 5 – 8Parasites, IchCupramineKeep copper concentration at 0.25 mg/l until the end of day 6 and then slowly increase to 0.50 mg/l another 20 drops, per 40 L), by end of day 8. Do not dose at once. Only keep adding Cupramine if fish are still feeding By end of day 8 copper concentration should be 0.50 mg/l. If fish are not feeding, consider holding fish in quarantine with no medication for a few days, then restart Cupramine treatment or maintain 0.25 mg/l for a few more days if the fish will eat at this concentration.
Day 9-23Parasites, IchCupramineEnsure concentration is maintained as you change 50% of the water every other day. Test copper daily and add cupramine as necessary. 
Day 24-30Flukes, Worms, Parasites,PraziproPerform a 100% water change, change filter media. Add Prazipro to tank – 1 tsp per 20 gal (75l) concentration. 50%  water change on day 28. Add half dose Prazipro after water change.
Day 31-38NoneNone100% water change with old display tank water. Continue feeding as usual, monitor fish, 50% water change every other day.
Day 39NoneNone If your fish are eating, behaving normally and have shown no signs of disease since they started quarantine, they are soon ready to move to the display tank. Begin to adjust food away from live mysis to main display tank food
Day 40NoneNone100% water change and feed with new food. Monitor for any changes. 
Day 42NoneNoneMove to display tank. Transfer fish one-by-one from the quarantine tank to a small container with old display tank water. Keep fish in this container for 5 minutes, then transfer fish (no water) to display tank. Feed fish once all new fish are added. Monitor existing fish for any aggression towards new fish. 

CONGRATULATIONS! You have completed quarantine for your new marine reef fish. Now you can rest assured that your fish will not be harbouring any diseases and your display tank will stay healthy and beautiful!

Note: If at anytime, your fish become sick and develop symptoms such as spots, lethargy, not feeding, bleeding, bulging eyes, you must identify that disease and medication needed. Perform a full water change in your quarantine tank and gradually begin to dose the medication for the disease. Treat all the fish together even if only one is showing symptoms as other fish are more than likely also infected. Early treatment before symptoms appear tends to improve chances of survival in unaffected fish.