Common name/s: Derasa Clam, Smooth Giant Clam Scientific name: Tridacna Derasa Family: Tridacnidae Origin: Indo-Pacific Maximum size: Up to 20" Care: These are excellently suited for aquarium use. They are the most widely available and the hardiest decorative clams in the aquarium trade today, their colours range from brown/gold to green/blue. Clams with a mainly brown mantle are more sensitive to light than other Tridacnids; as such they do better if they are placed deeper down near the substrate. They require strong lighting and a soft sand or crushed coral substrate to burrow into, to grow and bring out their colours. They also need good levels of calcium, strontium and iodine. The like a moderate water flow, not too strong and not to weak. They may be nipped by the likes of angelfish, blennies, shrimps, crabs, mantis shrimp, butterfly fish and others. Use caution when selecting unknown tankmates for propensity to nip at clams. Try to keep the specific gravity as stable as possible as Derasas don't like it to fluctuate too much. They will tend to move around until they find a spot suited to their needs. Sensitive to copper! Feeding: Zooxanthellate (photsynthesis by zooxanthellae cells in their mantle, so require strong lighting), they also need to be fed phytoplankton for them to grow quickly. Sexing: Within a year or two they will become hermaphroditic. Breeding: When these clams first become sexually mature they are males, not long after they become hermaphrodites which means they have both male and female reproductive organs. They normally release their eggs and sperm seperately to avoid self-fertilizing themselves, although this has been known to happen.