Velvet in fish is caused by parasites. Below is a quick overview of the fish disease.
What is the Velvet disease (Oodinium)?
The velvet disease (syn .: Oodinium pillularis ), also called “Oodinium” is a parasitic disease in fish that is cause by the following:
- Dinoflagellates pillulare Piscinoodinium (for freshwater fish)
- Amyloodinium ocellatum caused (in saltwater fishing)
Piscinoodinium pillulare reaches a size of a little more than 0.1 mm.
If you look at the infected fish obliquely from the front, lengthways (against the light), the skin appears cloudy and as if sprinkled with powdered sugar.
If you shine a torch on the fish in the dark, you can best see the infestation.
With a strong infestation the skin appears “velvety”, hence the name “velvet disease”. The color of this velvety covering is mostly golden-yellow. The gills of the infected fish are also very slimy.
Piscinoodinium pillulare only infects freshwater fish (in warm and cold water). In saltwater fish, Amyloodinium ocellatum (Syn. Oodinium ocellatum ) is considered to be the cause of the velvet disease or coral fish disease .
Infection with the velvet disease occurs mainly through newcomers. The parasite cannot survive longer than 24 without a suitable host.
The Velvet disease easily with the white spot disease can be confused, as many symptoms are similar.
Velvet disease (Oodinium) causes
Adult Siamese fighting fish (Betta splendens) infested with Piscinoodinium pillulare
Amyloodinium ocellatum feeds on the cell components of the (saltwater) fish.
In contrast, Piscinoodinium pillulare has photosynthetic abilities due to the chloroplasts in its cells.
Nevertheless, the skin of the fish host is massively damaged and dissolved by the root-like plasma threads.
Additional inflammation or fungal infections rarely occur. In the initial stage, the parasite spreads in the gills and causes the host fish to experience severe shortness of breath.
The fish skin can appear completely free of the parasite, and only when the cyst has been left does Piscinoodinium pillulare spread crawling over the entire skin surface.
The course of the disease is chronic over several weeks and difficult to detect even in a smear, as the parasite can hardly be distinguished from mucous membrane cells.
As the disease progresses, the parasite spreads en masse. This leads to a destruction of the cell network, combined with the death of the tissue, up to a rag-like detachment of the skin and bleeding within the gills. If the disease is not treated, the disease is always fatal after a long period of illness.
Velvet disease (Oodinium) Symptoms
Initial symptoms (before a visible infestation):
- increased or accelerated breathing (as in white spot disease )
- splayed gill lid
- Fish rub against the floor and objects (as in white spot disease )
- Refusal to feed, emaciation (as in white spot disease )
- unnatural secretion (as in white spot disease )
Symptoms of visible infestation:
- violent breathing frequency (as in white spot disease )
- slimy gills
- Fin clamps with rubbing movements (as in white spot disease )
- Fish stay near the surface of the water
- Fish stand near the movement of water
- velvety, powdered sugar-like topping
- Threads of mucus hang from the gills
- the skin peels off
Velvet disease (Oodinium) treatment
Since the velvet disease is a highly contagious fish disease, countermeasures should be taken immediately, as otherwise the entire fish population can be infected.
The development and life cycle of Piscinoodinium pillulare is highly dependent on the water temperature. The parasite takes longer to develop in colder water (e.g. in outdoor ponds) than in warmer water at temperatures of 25 ° C and above.
If the temperature is increased in order to accelerate the life cycle of the parasite, the fish can die from a lack of oxygen due to the massive spread in the gill tissue .
Treatment against Piscinoodinium pillulare in aquarium fish should be carried out without lighting due to the photosynthetic properties of this parasite.
Quinine hydrochloride (prescription only) or copper sulfate (be careful with catfish and lower animals such as snails or shrimp) are possible medications. In the over-the-counter trade, active ingredients with 2-amino-5-nitrothiazole are just as effective against Piscinoodinium pillulare . The advice of a qualified veterinarian should also be sought.