Velvet (fish disease)

Parasitic disease affecting fish

Illustration of Piscinoodinium

Velvet disease, also known as gold dust disease, is a common parasitic infection affecting freshwater and marine fish. It is caused by dinoflagellate parasites, primarily Piscinoodinium in freshwater environments and Amyloodinium in marine settings. This disease is characterized by a dusty, velvety appearance on the skin of infected fish, which is due to the presence of the parasites.

Causes

Velvet disease is caused by the protozoan parasites Piscinoodinium and Amyloodinium. These parasites attach to the skin, gills, and fins of fish, feeding on their host's cells and bodily fluids. The parasites are highly contagious and can spread rapidly in aquariums and fish farms.

Symptoms

Fish showing signs of velvet infection

Infected fish exhibit a range of symptoms, including:

• A fine, yellowish or gold dust-like coating on the skin and gills
• Rapid gill movement and labored breathing
• Clamped fins
• Loss of appetite
• Lethargy and erratic swimming behavior
• Rubbing against objects in the tank (flashing)

Diagnosis

Diagnosis of velvet disease is typically based on the observation of clinical signs and microscopic examination of skin and gill scrapings. The presence of the characteristic "velvet" appearance and the identification of the parasites under a microscope confirm the diagnosis.

Treatment

Treatment of velvet disease involves:

• Raising the water temperature to speed up the life cycle of the parasite
• Adding aquarium salt to the water
• Using copper-based medications, which are effective against the parasites
• Ensuring good water quality and reducing stress on the fish

Prevention

Preventive measures include:

• Quarantining new fish before introducing them to an established aquarium
• Maintaining optimal water quality
• Avoiding overcrowding
• Regular monitoring for signs of disease

Affected Species

Betta fry, a species susceptible to velvet disease

Velvet disease can affect a wide range of fish species. Freshwater species such as Bettas, guppies, and goldfish are particularly susceptible. In marine environments, species such as clownfish and tangs are commonly affected.

Related pages

• Ichthyophthirius multifiliis (Ich)
• Fish diseases and parasites
• Aquarium fish care