The Bicolor Blenny (Ecsenius bicolor) is an elongated, almost eel-like reef blenny found throughout the Indo-Pacific, from the Red Sea and Maldives region through Sri Lanka, the Philippines, and Micronesia and south to the Great Barrier Reef. It inhabits shallow reefs, lagoons, and rubble and crevice zones at depths of roughly 3 to 40 feet or more. The name refers to its striking two-tone pattern: a dark blue-gray, purple, or brown front half that transitions abruptly into a bright orange, yellow, or reddish-brown rear. Large protruding eyes topped with blue-rimmed cirri and comb-like grazing teeth complete the look. Adults reach about 4 to 4.5 inches, and males tend to grow larger than females, display more vivid blue coloration during breeding, and carry extended dorsal and anal fin elements.

Plan on a minimum of 30 gallons for a single fish, with 55 gallons or more if a pair is the goal. Maturity matters as much as volume here. A system that has been running for at least three or four months with visible diatom and film algae gives this grazer the natural forage it depends on, and specimens placed in sterile new tanks frequently decline. Build the aquascape from porous live rock arranged into numerous crevices, caves, ledges, and perches at varying heights, since this is a rock-dwelling hopper rather than an open-water swimmer and will quickly claim a favorite lookout.

Secure the rockwork with epoxy or careful stacking, because a Bicolor Blenny digs in the sand bed and shifts rubble and empty shells around its territory. A tight-fitting lid is not optional. This species is an accomplished jumper and is a well-known carpet surfer in open-top systems.