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About Velvet

Velvet disease, also called gold dust or rust disease is a fish parasite caused by the dinoflagellate parasites of the genera Oödinium, Piscinoodinium, Amyloodinium or Crepidoodinium which gives the fish a dusty, slimy look.

The parasite is single-celled and enters the slime coating or the gills 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 contagious 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.

  • Oödinium pilularis / Piscinoodinium pillulare is a freshwater parasite.
  • Amyloodinium Ocellatum is a marine parasite.


Seeing Velvet on a fish is very difficult. One tip is to darken the room and tank lights. Shine a flashlight or torch onto to the fish and you will see the light reflect off the velvet 'dust' around the head and gills.

  • Fish scratches against hard objects
  • Fish is lethargic
  • Loss of appetite and weight loss
  • Rapid, laboured breathing
  • Fine yellow or rusty coloured film on skin
  • Fins clamped against body
  • Mucus production increases
  • In advanced stages skin peels off


There are many off-the-shelf commerical treatments available from your local pet shop. The most effective chemical is Acriflavine. Though Copper sulphate, Malachite green can be used (with care).

Since freshwater Velvet photosynthesis make sure the tank is completely dark for 7 days. If the fish can handle it, raise the water temperature to 29C (84F).

Aerate well. This parasite attacks the gills and so the fish has trouble breathing.

Add Salt to the tank (if your fish can tolerate it).

Typical commercial products:

  • To clear a tank from Velvet remove all fish for at least 7 days. After that time all velvet will be dead.
  • Watch out for secondary infections from bacteria infecting the open sores of a treated fish. This can also kill. Treat with a antibacterial agent as well.

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