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.

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,

Cory

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