Cowfish are interesting looking fish due to their box-like body shape. Because of their body shape they are also known as boxfish. There are two kinds of cowfish, the scrawled cowfish (Acanthostracion quadricornis) as pictured above, and the longhorn cowfish (Lactoria cornuta). Both types of cowfish have horns above their eyes, but the longhorn cowfish has longer horns as the name suggest. Cowfish grow to approximately 18-19 inches or about 45-48 cm.
The longhorn cowfish can be found from Japan to Australia. The scrawled cowfish is found in the Atlantic. They feed on invertebrates and crustaceans. In captivity they will eat chopped meaty foods and marine algae. If kept in a reef aquarium they are likely to eat the inhabitants. They will also eat frozen food.
Cowfish are slow moving fish due to their body shape. They protect themselves by releasing a toxin. Because they can't escape the confines of the aquarium if a cowfish becomes stressed it may release this toxin poisoning themselves and your other fish in the process. In addition, if it dies the toxin will be released. If your cowfish becomes ill you should move it into a tank by itself.
Scrawled cowfish get along well with members of their own species as well as with other nonaggressive species. If you keep this fish with aggressive species it may release it's toxin as a defense mechanism.
Longhorn cowfish also shouldn't be kept with aggressive species or they may release their toxin, but they are also more solitary than scrawled cowfish and only young longhorn cowfish tend to congregate with their own kind. Adult longhorns are usually solitary. Another difference for longhorn cowfish is that they feed by using their mouth to blow away the substrate (generally sand) to expose the invertebrates living there.
Don't feed either one of the cowfish species floating or surface foods because this may cause them to ingest air. This will lead to buoyancy problems.