The Thorny Oyster is a member of the clam family. They are large and sessile with very colorful mantles. The Thorny Oyster's shell is shaped much like a scallop's shell, but the Thorny Oyster remains securely attached to the substrate on the aquarium floor, and does not wander. The Thorny Oyster is a reef safe invertebrate that is most often kept by the home aquarist as an ornamental element in the aquarium. The shell has many ridges and spines giving the Thorny Oyster an unusual, unique appearance. It is always best to quarantine the Thorny Oyster to be sure that you do not introduce any protozoan diseases they may have. The Thorny Oyster is very sensitive to changes in specific gravity, and requires strong water currents. The Thorny Oyster is a filter feeder that has its food brought to it on the currents in the aquarium. They should be fed daily with a dissolved, particulate organic substance (like Marine Snow), bacteria and phytoplankton. Provide calcium and alkalinity for best health.