To combat, do frequent water changes, siphon out detritus, and use a good protein skimmer. Commonly will contain fish wastes, fragments of rock, leftover food, among other things. Usually detritus will accumulate in low water flow areas, sumps, etc. Animals that eat detritus. Common detritivores are urchins, stars, hermits, etc.
Some fish have two dorsal fins one directly behind the other.
Means the animal lives in a certain place and nowhere else. In the taxonomy classification, the genus is the category ranking below a family and above a species. A fish with this condition will develop holes in its' head and sometimes along its' lateral line. The main cause is nutritional deficiency, especially vitamin C. Stress and poor water quality also play a role. Untreated cases will cause disfiguring or death.