Striped-fin Surgeonfish

Found in small schools, over surge zones, of shallow seaward reefs. Varies in colour with light.

Surgeonfish have a blade like spine in the tail that points outwards when bent, unicorns have two hook-like plates along the tail, these are used for defence and are as sharp as a surgeons scalpel, hence the name "Surgeonfish".
Some species are venomous.