Velvet (fish disease)

Velvet disease, also called gold dust disease is a fish disease caused by the dinoflagellate parasites of the genera Oödinium, Amyloodinium or Crepidoodinium which gives the fish a dusty, slimy look. The disease often infects fishes in tropical aquaria.

The parasite is single-celled and enters the slime coating of a host fish in its motile juvenile stage where it matures. The mature parasites break through the slime layer and drop to the bottom of the aquarium and attach themselves to solid surfaces. Here they form a cyst, which develops into numerous new juvenile individuals known as tomites.

Velvet is highly contageous and can prove fatal to fish. It is therefore important to treat as early as possible. The infected fish usually swims around scratching at things in the tank very rapidly and usually has its fins very close to its body.

The most effective medication for the treatment of Velvet is the substance called acriflavine, also called trypaflavine. The cures against Ichthyophthirius are somewhat effective but should be used longer than for the treatment of ich. As there is a chloroplast in the organism some prescribe to covering the tank completely to shut out all light while treating, thereby denying the free swimming stage a source of energy while it seeks a host. Acriflavine may work effectively without removing light, however.