Tridacna derasa (Derasa Clam) Care Guide
Tridacna derasa is a large smooth-shelled giant clam from the Indo-Pacific, hosting zooxanthellae and tolerant of more moderate light.
Overview
Tridacna derasa, the smooth or southern giant clam, reaches up to 60 cm in length. It is named for the relative lack of ribbing and scales on its thick shell, which shows six to seven vertical folds and lacks scutes. The mantle displays mixtures of orange, yellow, black and white, often marked with brilliant blue or green lines.
Taxonomy
- Family: Cardiidae
- Subfamily: Tridacninae
- Genus: Tridacna
- Scientific name: Tridacna derasa
Habitat
Its native range includes Australia, the Cocos Islands, Fiji, Indonesia, New Caledonia, Palau, Papua New Guinea, the Philippines, the Solomon Islands, Tonga and Vietnam. It is found on the outer edges of reefs at depths of about 4 to 10 metres.
Tank requirements
- Minimum tank volume: 400 L
- Temperature: 24-26 C (75-79 F)
- pH: 8.1-8.4
- Carbonate hardness (KH): 8-11 dKH
- Calcium: 380-450 ppm
- Magnesium: 1280-1350 ppm
- Specific gravity: 1.024-1.026
- Lifespan: 50-100 years
Diet
The species hosts symbiotic zooxanthellae that photosynthesise, allowing the clam to obtain nutrition from the water column beyond standard filter feeding. As a larger clam it tolerates more moderate lighting than crocea or maxima, while still benefiting from stable calcium, alkalinity and magnesium for shell growth.
Compatibility
It is peaceful and reef-safe among reef fish. Mantle-nipping species such as angelfish, triggers and pufferfish should be avoided.
Conservation status
IUCN Red List: Vulnerable. The species is listed on CITES Appendix II. It has been heavily harvested for food and the aquarium trade, although modern supply relies largely on aquaculture rather than wild collection.