Sleeper gobies are members of the Eleotridae fish family, found predominantly in the tropical Indo-Pacific, with about 35 genera and 182 species. While many eleotrids pass through a planktonic stage in the sea and some spend their entire lives in the sea; as adults, the majority live in freshwater streams and brackish waters. A few species (e.g., Milyeringa, Typhleotris, and some Bostrychus) are troglobitic. They are especially important as predators in the freshwater stream ecosystems on oceanic islands such as New Zealand and Hawaii that otherwise lack the predatory fish families typical of nearby continents, such as catfish. Anatomically, they are similar to the gobies (Gobiidae), though unlike the majority of gobies, they do not have a pelvic sucker.