- English Name : Lieutenant surgeonfish
- Local Name : Dhefah kaalhu
- Size : Max. 31 cm
- Family : ACANTHURIDAE
- Order : Perciformes
- Distinctive Characters: Dorsal fin with 9 spines and 23-24 rays. Anal fin with 3 spines and 22-23 rays. Pectoral rays 16. Body depth 1.9-2.2 in standard length. Body becoming more elongate with increasing size.
- Colour: Brown. Black marks behind eye: horseshoe-shaped in juveniles but becoming two separate stripes in adults. Caudal fin with white margin. Black area around caudal spine edged with pale blue.
- Habitat and Biology: Found on coral reefs at depths up to 20 m. Forms small schools. Grazes on benthic algae.
- Distribution: Western Indian Ocean.
- Remarks: Acanthurus tennenti is a fairly common shallow water surgeonfish. The colour of the sides can be changed from very pale brown (when the black “ear-stripes�? stand out very clearly) to a very dark brown (when they are almost invisible).