Slender filefish

Monacanthus tuckeri

Body laterally compressed, slender, and elongated. Variable shades of reddish brown to yellow-brown, brown or gray. Upper body usually darker. The color can change to blend with the background. Usually with a white reticulate pattern, but these markings may become indistinct (M. tuckeri). Large dewlap (extendable belly appendage) usually has a yellowish edge with a submarginal blue line.
Size up to 10 cm.
Slender Filefish Sep 13, 2017. Oil Slick Leap dive site in Bonaire. They can reach 10 cm but this one may have been a bit smaller. It floats upside down to mimetize with the soft coral rods. I will post a second pic where you can see the ventral fin. Caribbean Netherlands,Geotagged,Monacanthus tuckeri,Slender filefish,Summer

Distribution

Occasional Florida, Bahamas and Caribbean.
Slender Filefish Sep 13, 2017. Dive site Oil Slick leap, Bonaire. This is anotehr pic of the same fish as in previous spotting to show the colorful ventral fin. Caribbean Netherlands,Geotagged,Monacanthus tuckeri,Slender filefish,Summer

Habitat

Found over sandy and rocky bottoms, down to 50 m. Usually they live solitary or in pairs between gorgonians, sponges or near coral growths. Often they stay vertically in the water. Especially between gorgonians they are difficult to spot in this position. Feeds on algae and invertebrates.

References:

Some text fragments are auto parsed from Wikipedia.

http://species-identification.org/species.php?species_group=caribbean_diving_guide&id=182
https://reefguide.org/carib/slenderfile.html
http://www.iucnredlist.org/details/16781154/0
https://es.wikipedia.org/wiki/Monacanthus_tuckeri
Taxonomy
KingdomAnimalia
DivisionChordata
ClassActinopterygii
OrderTetraodontiformes
FamilyMonacanthidae
GenusMonacanthus
SpeciesMonacanthus tuckeri
Photographed in
Bonaire, Sint Eustatius and Saba