Velvet, or commonly known as the gold dust disease, if a fish disease that gives the infected fish a gold dust appearance when viewed at almost any light setting. This disease can affect any tropical fish and it also can effect some coldwater fish under certain situations. This disease is caused by species of Piscinoodinium inside of freshwater, while outbreaks inside slightly brackish water can be caused by Amyloodinium and Crepidoodinium species. Unlike many other different types of parasites, Piscinoodinium are partly photosynthetic and require a light source in order to survive. If left untreated this disease can lead to death of not only the infected fish, but also any other inhabitants that shared the same water.
Velvet is one of the most common parasitic diseases that is found within the freshwater hobby. Many of the fish that become infected are due factors such as if they are stressed when transported from the breeders to the fish store, and finally to your own setup, if they have come in contact with either a water source that has these parasites or fish that are infected being held within the same water column. In reality, every fish will come into contact with this parasite multiple times throughout its life, however in most cases the fish has a good immune system and/or has developed an immunity towards this parasite. Some of the major symptoms of velvet include a gold dust appearance when the fish swims throughout the water in light. As the disease progresses the fish might start to try to rub against decorations, the substrate, and any equipment that is inside of the fish's water column. This disease can cause the fish to become lethargic, breathe heavily and rapidly (when swimming or near the top of the water's surface), over develop their slime coat and lastly it can cause death if not treated.
In order to treat for velvet, we must first understand the life cycle that the parasites have. The first stage is what is known as the feeding stage where the trophonts live in the skin and/or scales of the fish and absorb nutrients from their blood stream along with photosynthesizing. In the proper tropical water temperatures, this stage can last up to six (6) days, with colder temperatures resulting in more days added to this stage. The second stage occurs when the trophonts start to mature into free form living tomonts that break out of the skin and scales of the fish, and start to swim around in the water column. The third stage is where the tomonts repeatedly divide to form up to 256 dinospores, which swim about in the water column looking for a new fish host to attach themselves to. If a host is not found within two (2) days then they will die, otherwise they will start this process all over again. The fourth and final stage that this parasite has it where the tomonts will keep on feeding off of the host, making the fish weaker and weaker immune system wise until it is either treated or dies off.
Treatment and Medication
There are several different medicines that will poison the free living stages of this parasite and kill it off within the water column. If the parasite is caught early on safer medicine can be used such as ones that contain acriflavine, or acridine. However if the parasite is not caught early on, tougher medicines that contain copper are highly effective. The only downside to using copper is that it is very toxic and/or lethal to many fish and invertebrates, along with most snails. When using any medicine, it is recommended to remove any carbon from the filter media and to also turn off any UV sterilizers or protein skimmers during usage. We recommend following the product's instructions on the bottle when using either of these products.
Due to the way that this disease spreads and effects the inhabitants, the best prevention methods are to always make sure that you quarantine anything that you place inside of your water (this includes any plants, inhabitants, decorations, and more). Thus, when you do let them adjust to your water and you truly see how they are acting, eating and if they have any symptoms or signs, we will either start to get a better understanding if they are infected, or learn about what possible other diseases they might have.