Most problems with fish health are related to water quality. Fish necropsy may be conducted to eludicate the cause of fish death. The cause of fish death may be chemical, biological, physical or any combination of these.
These broad categories include:
Oxygen levels in the water can drop below the level needed to support life. In low oxygen levels, physostomous fishes will try to survive by gulping air at the water surface. The size of the affected fish is significant. A fish kill caused by depressed oxygen levels will not include smaller fish unless critically low concentrations are reached.
Trauma related to explosions can cause detrimental effects not only to the fish, but also to the ecosystem. Surrounding habitats, such as coral reefs, are often damaged by explosions.
Toxins or poor water quality (industrial or domestic pollution, pesticides, fertilizers, oil, rapid thermal shift, changes in salinity, toxic algae)
Disease or population pressure (viral, bacterial, fungal, parasitic, spawning stress, over population)