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Marine velvet (Amyloodinium ocellatum)

The marine equivalent of freshwater velvet an extremely fast-moving dinoflagellate parasite causing gold or rust-colored dust on marine fish, rapid breathing, and quick death. Amyloodinium is considered one of the most dangerous diseases in the marine aquarium hobby and can kill an entire reef tank's fish population within 2–3 days if untreated.

Urgentpattern match not diagnosis2 source notes

Do first

  • Dim or black out the tank immediately Amyloodinium requires light for part of its life cycle.
  • Remove ALL fish to a hospital/quarantine tank immediately do not leave any fish in the display tank.
  • Do not treat the reef or display tank with copper. This will kill corals and invertebrates.
  • Treat fish in a separate fish-only hospital tank with copper or chloroquine phosphate.
  • The display tank (without fish) must go fallow (fish-free) for at least 72–76 days to break the life cycle.

Escalate if

  • Fish dying faster than they can be moved to the hospital tank.
  • Heavy gill involvement fish losing buoyancy and gasping severely.
  • No copper test kit available do not dose copper without being able to test levels.

Water clues

These readings can push this pattern higher or lower in the triage result.

ammonia above zero+3

Stress from poor water quality increases susceptibility.

temp above species max+3

Warmer temperatures accelerate the Amyloodinium life cycle.

Care protocol

Follow only the steps that fit your species, tank inhabitants, and medication label.

The fallow tank protocol

  1. Remove every fish from the display tank even fish that appear healthy are likely infected.
  2. Leave the display tank with invertebrates and corals but no fish for a minimum of 72–76 days (at 25°C/77°F).
  3. Maintain the display tank normally during the fallow period, just without fish.
  4. Treat all removed fish in a hospital tank with therapeutic copper or chloroquine phosphate for the full treatment course.
  5. Test copper levels daily in the hospital tank therapeutic range is 1.5–2.0 ppm free copper (ionic copper).
  6. Do not return fish to the display tank until the full fallow period is complete.
Cautions
  • Copper levels must be maintained within a tight therapeutic range too low is ineffective, too high is lethal.
  • Copper is irreversibly toxic to invertebrates never dose in a reef or invertebrate tank.
  • Chloroquine phosphate is an alternative that is less toxic but still effective. It is the preferred treatment for sensitive species.
  • The 72-day fallow period cannot be shortened significantly without risking reinfection.

Hospital tank treatment

  1. Set up a bare-bottom hospital tank with appropriate temperature and salinity.
  2. Add a cycled sponge filter or daily dose with ammonia detoxifier if uncycled.
  3. Dose with therapeutic copper (verify with a copper test kit daily) or chloroquine phosphate.
  4. Treat for a minimum of 30 days in the hospital tank.
  5. Perform small daily water changes to maintain water quality.
  6. After 30 days of treatment and 72 days of tank fallow fish can be returned.
Cautions
  • Do not rush Amyloodinium is extremely resilient and incomplete treatment leads to recurrence.
  • Do not add new fish to the display tank during the fallow period.
  • Do not share nets or equipment between hospital and display tanks.

Source notes

References and context notes used for this triage entry.

Amyloodinium ocellatum Merck Vet ManualVeterinary reference for marine velvet treatment protocols.Reef2Reef Marine Ich and Velvet Treatment GuideCommunity reference consult veterinary sources to verify treatment protocols.
Run Symptom CheckerCompare this pattern against water readings, affected count, and recent tank context.Ask AdvisorUse TankFlare Advisor to review this against your saved tank and recent logs.

Related patterns

Similar symptoms or risk factors worth comparing before treatment.

UrgentVelvet (Oodinium / Amyloodinium)

Fine gold, rust, or yellowish dust-like shimmer on the body and fins, often with intense flashing and rapid breathing. Caused by the dinoflagellate parasite Oodinium (freshwater) or Amyloodinium (marine). Often missed until advanced because the coating is subtle.

UrgentBrooklynella hostilis (clownfish disease)

A rapidly progressing skin ciliate that preferentially attacks clownfish (Amphiprion spp.) but can infect other marine fish. Causes excessive mucus, sloughing skin, rapid breathing, and fast deterioration. Often fatal within 24–48 hours without treatment. Can be confused with marine velvet but has a distinct slimy, sloughing appearance.

High priorityGill flukes or body flukes (Dactylogyrus / Gyrodactylus)

Rapid breathing, gill flaring, flashing, and scratching caused by microscopic monogenean parasites on the gills (Dactylogyrus) or skin/fins (Gyrodactylus). Often introduced with new fish. Requires microscopic confirmation for certainty but may be treated empirically when symptoms are consistent.

High priorityMarine ich (Cryptocaryon irritans white spot disease)

The marine equivalent of freshwater ich white salt-grain spots on skin and fins, with flashing and rapid breathing. Caused by the ciliate Cryptocaryon irritans. Nearly ubiquitous in marine aquariums and one of the most common diseases in reef tanks. The display tank must go fallow while fish are treated in a hospital tank, because Cryptocaryon cannot be treated safely in the presence of corals and invertebrates.