Distribution:
Mostly tropical and subtropical areas.
Habitat:
Marine, brackish, and freshwater.
Remarks:
Sleepers occur mostly in the Indo-Pacific region and primarily inhabit in fresh and brackish waters in the tropics. Relatives of the gobies (Gobiidae), they are characterized by having a short head and blunt snout, small conical teeth, smooth to rough scales, and pelvic fins entirely separated.
Sleepers have two spinuous dorsal fin with 2-8 flexible spines; six branchiostegal rays, and vertebrae 25-28. They mainly feed on benthic invertebrates, particularly crustaceans and grow to a maximum length of 60 cm.
This family contains two subfamily, Butinae and Eleotrinae, with a total of 35 genera and about 155 species.
References:
Nelson 2006; Robertson and Allen 2008