Very special thanks for the photo to Dr. Mark Erdmann.
Opistognathus rufilineatus, also known as Spotted Pug, typically reside in burrows they construct in sandy substrate. They will stuff their mouths with sand and spit it out elsewhere, slowly creating a tunnel. Using the protection of these burrows, these fish will hover, feeding on plankton or other small organisms, ready to dart back in at the first sign of danger. They are territorial of the area around their burrows.
Opistognathus rufilineatus are found mostly between coral rubble or sandy soils widespread in the Indo-West Pacific, Papua New Guinea and north-west Australia.