A large school of Rhabdamia sp. cardinalfish is a sight for sore eyes. Photo by MATTHEW OLDFIELD/SCIENCE PHOTO LIBRARY
The Luminous Cardinalfish (R.gracilis) is a sublimely beautiful little fish that forms impressive schools in the wild. They may not be the most colorful species, but a school of these cardinalfish live up to their name’s sake: Their reflective pigmentation create a entrancing dance of disco-ball light. Here is a video of a healthy school of R.gracilis from where else … Japan (B-Box Aquarium).
Luminous cardinalfish occur in shallow waters and have wide natural distribution – from the Indian Ocean to the Indo-Pacific all the way to the Marshall Islands.
Yet, they never make it into the American aquarium trade with any regularity.
Reefkeeping is trending towards natural displays with open aquascapes stocked with mated pairs or schools of conspecific fish (versus the old “collectors” mentality of adding as many individual fish of as many different species as the tank will fit). And while more and more US wholesalers and vendors are offering “paired” fish, we still lack a good selection of suitable schooling fish for the home aquaria. Reefkeepers are still largely resigned to the same tired selection of small schooling fish such as Chromis viridis, Zoramia leptacanthus cardinalfish, and the more recently available Red Spot Apogon parvulus cardinalfish.* But there are so many more species of chromis, cardinalfish, and other schooling fishes out there, and almost all of them are abundant in accessible shallow waters.
So wholesalers and fish vendors: Please consider importing more of these small schooling fish. Judging by how quickly red-spot cardinalfish sell at vendors like Liveaquaria/Diver’s Den, there is more than ample demand. I’d dare say reefkeepers are starved for good choices of schooling fish.
*Anthias were purposely omitted because, while schooling fish in the wild, most species tend to lose this behavior in captivity.