Gramma loreto is one of the most recognizable small reef fishes of the tropical Western Atlantic, splitting its body color into a vivid purple front half that dissolves into yellow or orange-yellow across the rear. A dark line runs through the eye, and a dark spot sits near the leading edge of the dorsal fin. The species ranges from Bermuda and the Bahamas south through Central America to northern South America, where it occupies caves, ledges, crevices and shaded reef walls. Adults reach roughly 3 inches.

Adult housing begins at 30 gallons, with the emphasis placed on structure rather than swimming room. Build substantial rockwork that includes caves, overhangs, narrow crevices and, ideally, a vertical reef-wall section that mimics the shaded faces this basslet naturally patrols. A fish placed in sparse aquascaping tends to disappear into whatever recess it can find and stay there, so multiple secure retreats close to the preferred territory matter more than open sand. Subdued or shaded shelter suits the species well. Keep the aquarium covered, as Royal Grammas are capable jumpers, and maintain stable tropical marine conditions.

One behavioral quirk worth anticipating is its habit of orienting its belly toward the nearest rock surface. Beneath ledges and along vertical walls this makes the fish appear to hover sideways or upside down, which is entirely normal and often the first sign that an individual has claimed a particular overhang as home.