Bats

The adults of this small family of large, rounded, diver-friendly fish are often seen in small groups at cleaner stations on the reef, or in larger aggregations mid-water close to drop-offs.

The young look quite different with their very elongated dorsal and anal fins. They stay close to the bottom or close to floating objects. Platax orbicularis juveniles mimic dead leavesmleaves, while the zebra-stripes of P. batavianus break up their form.

The spectacular jet-black young of P. pinnatus have brilliant orange margins to all their fins and body. The young juveniles in particular, swim in the dark recesses of bommies covered in many corals. As such they are quite difficult to make out as you do not see a fish, just orange lines moving in a dark hole. The flatworm "Pseudobiceros hankockanus" is also black with an orange margin, and it is often suggested that the juvenile batfish mimic these flatworms as they are poisonous.

There is only the one genus in this small family of common reef fish. They have a very characteristic overhanging upper lip, and very small scales. The body shape is similar to surgeonfish.

They feed mostly on seagrass and benthic algae, but some species consume quanitites of sponges and tunicates.

Surgeonfish get their name from razor-sharp spines or keels at the base of their tails. In the Lined Surgeonfish (Acanthurus lineatus), these are poisonous. A number of species are able to change their colour very quickly.

Some (e.g. Acanthurus mata) come together in large schools while most are either solitary or seen in small groups. Most are algae-feeders, and are in fact the dominant reef vegetarians, playing an important role in the reef ecosystem. Members of the genus Naso feed on plankton mid-water.