This is a Bridled Goby, which is just one of the many (more then 2200 species or approximately ten percent of the total number of teleost fishes) on earth. Gobies can be found throughout most of the tropical, subtropical and temperate regions of the world, occurring in a variety of habitats in fresh, brackish, and coastal marine waters to depths of about 600 feet. Most species are benthic, some are pelagic, many are burrowers, and many live in burrows constructed by other animals.
A lot of gobies live in sponges, some live on cave ceilings (where they have to swim upside down). Some migrate upstreams and even climb waterfalls as high as 300 feet. Some are blind. Some can change their sex. Gobies may be really tiny – less then 0.9 cm. One variety of goby is the smallest vertebrate in the world, one is the smallest freshwater vertebrate and a third is the smallest vertebrate in weight.