For educational purposes only. This page does not provide medical or veterinary advice, diagnosis, or treatment. Always consult a qualified healthcare or veterinary professional before making any health-related decisions.
Marine Velvet
Amyloodinium ocellatum
Size: Microscopic — trophonts 20–350 µm; visible only as velvety film on fish
One of the most common and deadly diseases in saltwater aquariums worldwide; also occurs in wild marine fish; can kill an entire tank within days if untreated
Amyloodinium ocellatum, commonly called marine velvet or coral fish disease, is a parasitic dinoflagellate (a type of single-celled organism related to algae) that infects the skin and gills of saltwater fish. It is considered even more dangerous than marine ich — it spreads faster, is harder to see in early stages, and can kill fish within 24–72 hours of heavy infestation. Infected fish develop a characteristic gold or rust-colored dusty coating (like velvet fabric) on their body and fins. It is one of the leading causes of fish death in marine aquariums.
Lifecycle
The lifecycle mirrors marine ich but is faster and more aggressive. Trophonts (feeding stage) attach to fish skin and gills, feeding on cells. They drop off as tomonts, which divide rapidly in cysts on the substrate — producing up to 256 dinospores per cyst. Free-swimming dinospores must find a host within 24 hours or die. The full cycle can complete in as little as 7–10 days at warm temperatures, allowing explosive population growth.
Marine Velvet — Amyloodinium ocellatum
Symptoms
Pharmaceutical treatments
Evidence-based medications used by healthcare and veterinary professionals.
Reference only. Medication names, types, and notes are provided for general awareness. Dosage, suitability, and prescribing decisions must be made by a licensed physician or veterinarian.
Copper sulfate treatment
Aquarium treatmentThe most effective treatment. Maintained at 0.15–0.20 ppm free copper for 4 weeks in a hospital tank. Toxic to invertebrates and corals — never use in a reef tank.
Chloroquine phosphate
Aquarium treatmentHighly effective against Amyloodinium. Dosed at 40 mg per gallon in a hospital tank. Less stressful than copper for some fish species.
Formalin bath
Aquarium treatmentShort-term bath treatment that kills trophonts. Requires precise dosing, strong aeration, and close monitoring. Used as an emergency measure or alongside other treatments.
Holistic & natural approaches
Traditional, herbal, and integrative approaches for general awareness.
Not a substitute for medical treatment. Natural remedies listed here have not been evaluated by the FDA or equivalent regulatory bodies. Do not use these in place of prescribed treatment. Always consult a qualified healthcare or veterinary professional first.
Tank fallow period (display tank)
Remove all fish from the display tank for a minimum of 8 weeks (at 80°F/27°C). Dinospores die without a host. Invertebrates and corals can remain. This is the most reliable non-chemical approach for the display tank.
Hyposalinity
Reducing specific gravity to 1.009–1.010 may slow Amyloodinium but is less effective than against marine ich. Some strains tolerate low salinity. Not recommended as a sole treatment for velvet.
Darkness treatment (supportive)
Amyloodinium is a photosynthetic organism and requires light to thrive. Keeping the hospital tank in complete darkness for 3–4 days can weaken the parasite and is used as a supportive measure alongside copper or chloroquine treatment.
Prevention
Zoonotic risk — low or none
Amyloodinium ocellatum does not infect humans. It is exclusively a parasite of marine fish and poses no human health risk.
Related parasites
Marine Ich
Cryptocaryon irritans
Cryptocaryon irritans, commonly called marine ich or white spot disease, is a ciliated protozoan parasite that infects the skin, fins, and gills of saltwater fish. It is the marine equivalent of freshwater ich (Ichthyophthirius multifiliis) and is one of the most common and devastating diseases in saltwater aquariums. Infected fish develop characteristic white spots (trophonts) visible on the body and fins. The parasite is highly contagious and can wipe out an entire aquarium if untreated. It does not infect humans.
Neobenedenia
Neobenedenia spp.
Neobenedenia are parasitic flatworms (monogenean flukes) that live on the skin, fins, and eyes of marine fish. They are among the most economically damaging parasites in marine aquaculture, causing massive losses in sea bass, grouper, snapper, and other farmed species. Neobenedenia are hermaphroditic, reproduce rapidly, and can complete their entire lifecycle on a single fish host — making population explosions possible in the confined conditions of fish farms and aquariums. They feed on skin cells and mucus, causing lesions, eye damage (sometimes blindness), and secondary infections.