Marine Velvet (Amyloodinium): symptoms, treatment, prevention

Amyloodinium ocellatum is a highly virulent dinoflagellate parasite of marine fish that primarily attacks the gills and causes rapid mortality.

Overview

Marine Velvet is caused by Amyloodinium ocellatum, a dinoflagellate parasite. It is one of the most acute killers in marine aquaria: fish often die from gill suffocation before the characteristic gold dust coating becomes visible to the naked eye.

Symptoms

Fine gold or dust-like coating on the body
Extremely rapid gill respiration
Gasping at the surface
Hiding and refusing food
Sudden mortality
Scratching against decor

Causes

The parasite is introduced through new fish, contaminated water, or shared nets. Free-swimming dinospores rapidly attach to gills and skin, and a single infected fish can seed an outbreak in days.

Diagnosis

A very fine dusty coating combined with extreme respiratory distress in marine fish suggests velvet. Differentiate from marine Ich (coarser discrete spots) and Brooklynella (heavy sloughing slime) by microscopy of a gill or skin scrape; affected fish often die before classic skin signs are obvious.

Treatment

Speed is critical. Move every fish to a bare-bottom quarantine immediately and treat aggressively; the display tank cannot be safely medicated due to invertebrates and live rock.

Quarantine

Use a bare-bottom quarantine with strong aeration, mature filtration and a heater. Leave the display fallow without fish for at least eight weeks so dinospores starve without a host.

Medication

Copper sulfate or chelated copper at 0.5 ppm in bare-bottom quarantine for 14-21 days, with daily copper test monitoring; lethal to invertebrates.
Chloroquine phosphate at 40-60 mg/L as a single dose for 30 days, preferred when copper is contraindicated.

Recovery

Maintain oxygen levels high and feed enriched food to rebuild gill tissue. Do not return fish to the display until the full course is finished and the display has remained fallow for the recommended period.

Prevention

Strict 6-week marine quarantine
Do not share nets or equipment between tanks
UV sterilizer to reduce dinospore load
Avoid stress that compromises mucus coat