Pholidichthys leucotaenia Pholidichthys leucotaenia Pholidichthys leucotaenia, commonly known as the convict blenny/goby or the engineer blenny/goby, is a marine fish from the west-central Pacific Ocean. It is neither a blenny nor a goby, but is in fact one of two species in the family Pholidichthyidae. A small eel-shaped fish, it can grow up to in length. Juveniles resemble the striped catfish "Plotosus lineatus", which is venomous, having a black body with a white dorsal stripe. As they develop, the stripe changes to white convict-style barring or spotting in the adult. It lives in shallow lagoons and on coastal reefs from the Philippines
Sand goby rounded. In males, there is a conspicuous dark spot on the anterior dorsal fin and in both sexes there is a black patch on the caudal peduncle. The general colour is sandy brown with indistinct dark blotches and reticulations on the dorsal surface and dark striations on the pale fins. The colour of the male darkens during the breeding season and his fins become more coloured. The average size is about . The sand goby normally lives at greater depths than the common goby. It feeds on small invertebrates living on the seabed especially amphipods. It is well camouflaged and