Tridacna is a genus of large saltwater clams, marine bivalve mollusks in the subfamily Tridacninae. They have heavy shells, fluted with 4–6 folds. Mantle is brightly coloured. They inhabit shallow waters of coral reefs in warm seas of the Indo-Pacific region.These clams are popular in marine aquaria, and in some areas, such as the Philippines, members of the genus are farmed for the marine aquarium trade. They live in symbiosis with photosynthetic algae (zooxanthellae). Some species are used as seafood.