What do molluscs eat?

Molluscs eat all kinds of things. The cephalopods (octopi, squids, and their allies) are predators of fish and other marine life. Most bivalves are pretty much herbivorous, feeding primarily on phytoplankton, though some are predators. The gastropods are also mixed, with some herbivorous, such as abalones, and some carnivorous predators, such as moon snails, oyster drills, and cone shells. Incidentally, some cone shells (Family Conidae) are poisonous enough to kill people! They also eat snails.