Thompson's Surgeonfish

Found singly or in small schools, over coral and sandy areas, along steep drop-offs and steep outer reef slopes. Can change colour when disturbed.

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.