They are small tropical fish associated with coral and rocky reefs in the Atlantic, Indian and Pacific Oceans.

The head has a blunt snout, a small, terminal mouth, a nostril on each side of the face, and large eyes.

They tend not to face too much competition from other fish because of the very shallow water in which they live and because their habitat is not actually on reefs, but is near them, among boulders, dead branching corals, man-made structures, and junk.

The male fertilises them and then stays to guard them, removing any debris that lands on them or unfertilised eggs and fanning the developing embryos with his fins to keep them well oxygenated.

They will indeed tolerate poor water quality and feed on the algae which is often a nuisance in reef tanks, but because of their aggressive behaviour, they should not be kept with other fish, especially smaller ones.