Marine velvet is as the name suggests a disease that is found in saltwater aquariums and it is one of the most common illnesses in saltwater aquariums. It can infect fish in all different types of saltwater aquariums from species tanks to reef tanks, from coldwater tanks to tropical tanks. Marine velvet is found in all the oceans of the world and is common in wild-caught fish. The disease infects stressed or weakened fish and is therefore common in newly transported and recently caught wild fish. The disease only seldom affects healthy fish but can infect healthy fish if they are kept in an aquarium with an already infected fish.
Marine velvet progresses fast and can quickly kill fish; it is therefore very important to spot and treat the disease as fast as possible. The symptoms include quick breathing (the fish breathes faster than normal) and "dust" on the body of the fish. This dust can be a number of colors but is usually white, grey, brown or yellow. Observe that dust doesn't mean spots; white spots on the fish are instead a symptom of the other common marine disease - saltwater ich. Other symptoms of marine velvet are fish scratching themselves against the aquarium decoration and loss of apatite. The disease usually kills fish by damaging their respiratory system. Marine velvet is very contagious and is fatal unless treated.
There are several methods to threat this marine velvet. One is to move infected fish to a hospital aquarium where the salinity is lowered. This will cure the fish as marine velvet can't survive low salinity. It can however put a strain on the fish and it can be hard to reintroduce the fish to higher salinity levels. Some fish species are also less tolerant than others of low salinity. You have to be able to accurately measure and manipulate salinity to use this method. Another option is to use copper to treat the disease. If using a copper based medicine you should always follow the instructions and make sure that you don't keep any organisms that are sensitive to copper in your aquarium.
