Serranus tortugarum is one of the smallest members of the sea bass family (Serranidae sp.). They're from the Caribbean, and attain a maximum length of 3", although I rarely see specimens much larger then 2" in captivity.
They're planktonivores, and live in small aggregations in the wild. Like most members of this family, they're true hermaphrodites. A pecking order is established, and the dominant specimen becomes the male (much like anthias).
They spend the majority of their existence close to the substrate, and seldom venture far from the sandbed/rocks.
A moderately hardy species, on par with some of the hardier anthias species. Feed often with fatty/meaty foods. 2-4 times a day is preferable. Live foods (eg artemia "brine shrimp") may be needed to initiate captive feeding.
Great reef-safe fish.
I believe Scott Michael's book includes this species, and may have more information.
