Velvet in Aquarium Fish

10.2.3. Velvet in Aquarium Fish

“Velvet” (Piscinoodinium pillulare, or “oodinium”, a dinoflagellate algae) is a very small parasite that looks like tiny spots of yellowish to golden-brown or rusty-colored varnish on the fish.

Well-intentioned but ill-informed commentators on the social media are constantly identifying patches of white on fish as “velvet”. They are simply wrong. “Velvet” has a distinctive gold pigmentation. “VELVET” HAS TO BE GOLD COLORED. If there is a patch of white it will most often be bacterial (typically but not always columnaris bacteria). A patch on the forehead of a fish can also be tetrahymena. Hundreds of very small white dots can be chilodonella, costia, epistylis or tetrahymena. If the patchiness or spots are white it will NEVER be true “velvet”.

Note that many well-intentioned but ill-informed commentators on betta forums are constantly saying that a betta with a frayed tail and/or gray patches on its body has “graphite disease” and that “graphite disease” is a type of oodinium. This is not true. “Graphite disease” is either a type of mycobacterium (“Fish TB”) or a bacterial disease like columnaris. And true “graphite disease” (an unusual mycobacterium) ONLY occurs in blue or blue-black bettas. More about this disease can be found at this link:

10.16. Graphite Disease in Blue Bettas

Oodinium or “Velvet”
Oodinium or “Velvet”

The definitive diagnosis of “velvet” requires a microscope. But given that virtually all the “white dots”, “gold dots” or “small dots” are treated exactly the same way, the microscope really isn’t required.

The disease is very similar to ich in how it progresses, with three stages; an infectious stage on the fish, a stage which falls to the floor of the aquarium and multiplies, and a small free swimming stage which attaches to the fish.  Like ich, it affects the gills initially and can thus be difficult to diagnose in its early stages.

Velvet (oodinium) on the fish
Velvet (oodinium) on the fish.

Treating Velvet

Treating velvet is actually very easy. The treatment is identical to that used for ich. 

  • Add lots of additional biofiltration (under-gravel, canister or sump) to filter out and thus kill the free-swimming organisms. This added biofiltration also reduces the bacterial loading in the water which in turn allows the fish to devote more immune system resources to the pathogen.
  • Add a formalin/malachite green medication (Ich-X, Rid-Ich Plus, Blue Planet White Spot Remedy and Mardel QuickCure) or a Copper based medication (Cupramine, Copper Power, Copper Aide or Copper Safe) to the water of the aquarium to kill the free swimming organisms.
  • Do not put the fish in a hospital/quarantine tank
  • Do not change out or clean the filter media.
  • Do not raise the temperature of the tank
  • Add a 24/7 UV sterilizer to kill the free swimming organisms and reduce the bacterial loading in the water which in turn allows the fish to devote more immune system resources to the pathogen.
  • Added aeration always is helpful

This disease is very rare in tropical freshwater aquariums. Over many years and literally thousands of diseased fishes I’ve seen on social media and fish forums, I have seen only a single case of velvet (the peacock below).

Velvet on a Cichlid
Velvet on a Cichlid

Note that the idea that “scaleless” fish need a half dose is a myth. All fish do just fine with a full dose.  Two owners of fish stores and acknowledged experts on fishkeeping (Vicki of Freshwater Aquariums and Cory of Aquarium Co-op) have both treated thousands of scaleless fish with several full-strength medications with no problems.

If you have invertebrates (snails, shrimp) the copper will kill them, so the only safe medication is formalin and formalin malachite green combination. Copper is also dangerous in very soft water (GH< 4).

Startpage Aquariumscience

Source: – David Bogert

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