fish

Velvet Disease (Oodinium)

A parasitic disease caused by Oodinium that produces a fine, gold or rust-colored dusting on the fish body. Highly contagious and often fatal if untreated promptly.

Symptoms

Fine golden or rust-coloured dusting over body and fins, most visible under bright light.
Fish flicking and rubbing against objects, rapid breathing, clamped fins.
Loss of appetite and lethargy; heavy infections damage skin and gills.

Common Causes

Parasitic Oodinium infection — freshwater and marine forms are distinct parasites (conflict noted: confirm which form applies).
Stress, temperature swings, and poor water quality let the parasite multiply rapidly.
Introduction of new fish without quarantine (E1: highly contagious, often fatal if untreated promptly).

What to Check

Look for the gold film under strong light — it is easy to miss in dim conditions.
Quarantine new fish and check every tank inhabitant for early signs.
Confirm freshwater vs marine form before choosing medication — treatments differ.

What Not to Do

Do not delay — velvet is highly contagious and often fatal if untreated promptly (E1).
Do not use a freshwater velvet treatment in a saltwater tank (or vice versa) without confirming the label.

This guide is informational and does not replace professional veterinary advice. If fish are severely ill, consult a veterinarian.

Velvet Disease (Oodinium)

Symptoms

Common Causes

What to Check

What Not to Do

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Velvet Disease (Oodinium)

Symptoms

Common Causes

What to Check

What Not to Do