Triggerfish and Filefish
Oblong or lozenge-shaped bodies, very sharp teeth, and bizarre markings are among the physical characteristics of members of this family. However, the most distinctive feature that these fish have is what gives them their common name. The name triggerfish is very descriptive - the "trigger" is part of the mechanism that locks the dorsal fin into the upright position. This is either to prevent the fish from beong swallowed by a predator, or to help wedge it in a crevice from which it cannot be moved, until it releases the trigger to lower the fin. When puchasing a triggerfish, don't refuse to buy it on the grounds that its pelvic fins have broken off, as it doesn't have any.
Photo courtesy of www.tjorvar.is
The clown trigger tends to become aggressive, and requires plenty of well-anchored retreats. It is omnivorous and needs a tank on its own (36 gallon at least), or with other large fish. In the wild it can reach 20 inches in length, in captivity it is usually 4.5 inches long. The optimum water temperature is about 79F.
Triggerfish are both solitary and territorial which, in terms of aquarium culture, means that they need space if quarrels are to be avoided between similar species. As well as needing space, they also require retreats and places to rummage in. Make sure the aquarium decorations are fixed firmly in place as these fish will attempt (and usually succeed) in rearranging the substrate and other "fixtures and fittings" if they got a chance.
They will assume that anything is good to eat and will attempt to chew at it, so their inclusion in a mixed fish and invertabrate collection is not a good idea. Because triggerfish are not fussy feeders this makes feeding unproblematic, but take care their sharp teeth don't have a chance to get a taste of you when maintaining the aquarium.
Their relations, filefish, differ in that they are unable to lock the first dorsal spine into an upright position. They have extremely rough skin and are known by the alternative popular name of "leather-jackets."