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Dealing with Marine Velvet

Hi, Cory here. One challenge often faced by aquarists is keeping your fish free of parasites and disease. If your fish become sick you have to learn how to treat them effectively. There are so many pathogens in the aquatic world, from parasites to bacteria and fungi. Probably the most common infestations that plague aquarium keepers are Marine Ich (Cryptocaryon irritans) and Freshwater Ich (Ichthyophthirius multifiliis). These afflictions are easy to spot, and relatively easy to treat depending on the type of fish and aquarium setup. There is another parasite which I’m addressing today that is common though frequently overlooked or misidentified. Marine Velvet maybe just as common as Ich, but is rarely diagnosed in time to save the fish.

Marine Velvet (Amyloodinium ocellatum) is classified as a dinoflagellate, not a protozoan, since it takes on some algae characteristics. Without going into too much detail, Amyloodinium is still a parasite and quite a nasty one at that. Once established in an aquarium, the parasite will continue to reproduce infecting every fish without immunity to it. Though sharing similar life cycles with Ich, the visible effects are noticeably different. Marine Velvet’s common symptoms are heavy breathing, loss of appetite, flashing/scratching, and eventually a white, hazy film on the body of the fish. When the film appears the infection is advanced, and without immediate treatment the fish will most likely not survive.

Coppersafe The most common and effective treatment on the market is copper, but copper treatments have some down sides. Some fish cannot tolerate exposure to copper, and it is lethal to invertebrates. It has the potential destabilize the natural balance of your aquarium. The effective dose is between 0.15 to 0.20 ppm for around 15 days, and it is highly recommended that you treat the infected fish in a quarantine tank. Although effectively curing the fish, this treatment does not eliminate the parasite in the main aquarium, which may be waiting to attack your fish when put back into the tank.

Velvet has a rather complex life cycle which can make it very difficult to eradicate completely. When the parasite is attached to the fish, it is called a trophont. Once the parasite detaches, it is considered a tomont. The tomonts divide, creating up to 256 new, free-swimming, infectious individuals called dinospores. The dinospores attach and begin to feed on the fish.Then the cycle begins again. The length of this cycle can vary from as quickly as 3 weeks to as long as 6 weeks, but generally about 4 weeks given normal tank conditions.

Knowing the complete life cycle of the parasite, the only way to eradicate it in all life stages is to remove all of the fish from the aquarium.  Without a fish host, the parasite will be unable to complete the trophont part of the cycle and the organisms will perish.

As with any infection, prevention is the best way to go. The best way to prevent a marine velvet outbreak is to quarantine new fish for at least 4 weeks. That may seem like a long time, but the amount of time and money that can be involved in treating the infection makes quarantining well worth the effort. If your quarantined fish shows symptoms of marine velvet, you can effectively treat them using copper without disrupting of damaging your show tank. No matter what type of aquarium you have, quarantining all new fish will decrease problems from pathogens exponentially.

Thanks, until next time,



  1. avatar

    hey there cory i have a question for u. okay here it goes now my fish keep on dieing and i believe that this is what they have. now will my coral also die as well and also is it always going to be in my tank once i have gotten it. thanks josh

  2. avatar


    Marine velvet will not affect you corals or other invertebrates, just the fish. The parasite will remain in your aquarium as long as there is a fish (host) to continue it’s life cycle. If you would like to get rid of the parasite, you will have to remove all of your fish from the aquarium, letting the tank run without fish for up to 40 days. The fish that you quarantine should be treated with copper to insure that they are no longer carrying the parasite.

  3. avatar

    I have been trying to fight velvet for months and it still comes back. 4 weeks, then 5 weeks, then almost 6 weeks and complete failure every time. Now I’m going to try 8 weeks. I’m taking all my fish out except my snowflake eel. The question I have I can’t seem to find on any site so I’ll see if you can help me. WILL VELVET STILL REPRODUCE IF THE SNOWFLAKE EEL IS STILL IN MY MAIN TANK? Please respond whenever you get the chance, thanks

  4. avatar

    Justin, Eels are generally not susceptible to most fish parasites because of their heavy slime coat. 4 weeks should be a sufficient amount of time to allow your tank to go without fish to eliminate most parasites. If this is happening repeatedly, I would look to other potential sources of stress, like water quality as key factor in what is going on.

  5. avatar

    I lost all my fish to velvet with the exception of my yellow coris wrasse about two weeks ago. I still have the wrasse in my main tank and I’m trying to decide if I should pull the wrasse out and give him a copper treatment. The wrasse looks very healthy eating like a pig and has no indications of velvet. Looking forward to your suggestion. Thanks

  6. avatar

    Hi Charles, I would give it at least about 4 weeks of observing the fish. The average lifestyle of this parasite is usually around 2-3 weeks and may take some time to show signs on your fish. For the main tank, you can either treat the tank or remove the fish that you have left into a quarantine system for a few weeks to make sure the parasite isn’t just waiting for another chance to break out again.

  7. avatar

    The signs of Marine Velvet infection are rather subtle. Respiratory difficulties seem to be one of the most common signs. Other signs are a decrease or a complete loss of appetite, rubbing against objects in the aquarium, erratic swimming behavior, and a dusty or dull velvety sheen, from which this disease gets its common name.

  8. avatar

    All my fish died from velvet except the snowflake eel….if I leave him in the display tank will the velvet ,die or do I have to quarantine him thanks

  9. avatar

    Hello Anonymous, Velvet typically doesn’t affect eels because of their thick slime coat and leaving the eel in the tank without any other fish should be sufficient to break the life cycle of the Velvet.

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About Cory Shank

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Cory is one of our Staff Marine Biologists and has been with the company since 1999. He has always had an interest in fish and inverts started soon after his employment began, and laid the path for him to earn his Marine Bio degree From Millersville University just a couple of years ago. Since graduation, Cory has been propagating many different corals including LPS and SPS and maintaining both his own reef aquaria and several at our retail store. His interests besides propagation include snorkeling, environmentalism, travel, and anything relating to reefs and oceans.