Brooklynella (Clownfish Disease): symptoms, treatment, prevention

Brooklynella hostilis is an aggressive marine ciliate parasite that causes severe slime sloughing and gill damage, especially in clownfish and seahorses.

Overview

Brooklynella, often called "Clownfish Disease", is caused by the ciliate Brooklynella hostilis. It is particularly devastating in newly imported wild-caught clownfish and in seahorses, with mortality possible within 24-48 hours of clinical signs.

Symptoms

• Thick white slime sloughing off the body
• Gasping at the surface
• Loss of color
• Rapid breathing
• Skin ulceration
• Death within 24-48 hours if untreated

Causes

Most outbreaks trace to wild-caught imports stressed by collection and transport. Poor quarantine and shared equipment accelerate spread.

Diagnosis

Heavy white sloughing mucus and rapid respiratory collapse in clownfish or seahorses are typical. Microscopy of a skin scrape shows kidney-shaped fast-swimming ciliates, distinguishing Brooklynella from marine Ich (white spots) and velvet (fine gold dust).

Treatment

Act within hours. Move affected fish to a quarantine tank and use either formalin or chloroquine; the display tank should be left fallow afterwards.

Quarantine

A bare-bottom hospital tank with strong aeration, mature filtration and stable salinity is mandatory. Treat new clownfish prophylactically on arrival even without symptoms.

Medication

1. Formalin bath at 150-250 ppm in an aerated container for 45 minutes daily for 3-5 days in quarantine.
2. Chloroquine phosphate at 40-60 mg/L in quarantine for 14-21 days; safer for prolonged exposure than formalin.

Recovery

Provide enriched food and minimise handling stress during recovery. Hold fish for the full quarantine period before returning them to the display.

Prevention

• Always quarantine clownfish and seahorses
• Avoid wild-caught specimens when possible
• Treat prophylactically in quarantine on arrival
• Monitor newly imported fish closely