A barred sand-and-rubble pipefish with a red, white-edged tail, almost always in pairs.
To about 18 cm, pale tan to cream with fine reddish-brown bars and reticulations along the body, a series of narrow bars across the snout, and a red caudal fin with a white margin, which is what the species name refers to. The network pipefish, Corythoichthys flavofasciatus, is the usual confusion: it is a little smaller, to about 15 cm, and its markings are a finer net rather than distinct bars. Across the genus, snout markings and caudal fin colour separate species more reliably than body pattern, which varies within a species and changes with the bottom the fish is on.
Sand, rubble and the margins of reef from the shallows to about 25 m, working over the bottom in short glides rather than hovering in open water. Pairs are the rule. In this species the pair bond has been followed in the field: the two fish meet each morning within a small shared range and repeat the meeting daily, which appears to keep them synchronised for breeding. The male carries the eggs on the underside of the tail in a shallow pouch rather than a sealed one, so a carrying fish shows the eggs plainly from the side.
The name messmate pipefish is applied loosely to several members of the genus, so it is worth reading a record as a genus-level identification unless the caudal fin is described or shown.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.