Rock Beauty Angelfish (Holacanthus tricolor)On one of my earliest dives down in the Florida Keys back in the 1990s, a gorgeous yellow and black angelfish caught my attention as I drifted over a section of reef. In my mind’s eye, I envision the angel hovering boldly above a large barrel sponge, but I can’t be sure whether that’s actually how it happened or just an idyllic memory. In any case, I was taken with its distinctive appearance and wondered whether it might make a good aquarium candidate. As anyone familiar with the fauna of the tropical western Atlantic has already guessed, the angel I saw back then was a rock beauty (Holacanthus tricolor)—a species that, unfortunately, tends to fare poorly in marine aquaria and is generally best left to advanced fishkeepers or, better yet, in the ocean where it can beguile other divers. I’ll get into why in just a moment.Physical traits H. tricolor is laterally compressed (flattened from side to side) and, in typical angel fashion, sports a sharp, backward curving spine on the gill cover (operculum). As alluded above, this species is yellow on the anterior portion of the body and on the caudal fin and black from behind the gills to the caudal peduncle (base of the tail). The margin of the anal fin, the edge of the operculum, and the opercular spine are orange.
From the boat, there’s nothing remarkable about the place — just choppy water and a white mooring ball, a few miles offshore. But once we’re underwater, I can see the rows and rows of PVC trees, suspended above the sand in a grid that stretches away into the distant murk. This is a coral nursery. Each tree bears a ripening crop of a hundred or more pieces of coral. The smallest fragments are pinkie-sized, twirling on their tethers as other divers kick by; the largest hang like many-limbed chandeliers, turning slowly in the current. When I get closer, I can see the individual polyps, the anemone-like creatures that make up each fragmented colony. Nestled in the crenellated openings in their solid skeletons, they