Clams are terrific additions to any reef aquarium, but their large, fleshy mantles have a tendency to really draw out the nippers. Many angelfish and butterflyfish just can’t resist nibbling on a clam’s mantle tissue, and while the clam can survive the occasional bite here and there, they won’t last long if the nipping doesn’t stop. Initially, a clam that is being picked on will just retract until it no longer feels threatened. But over time, the clam will stop coming back out. This shut-in behavior prevents it from receiving the sunlight and nutrients needed for survival, and combined with the stress of being bitten over and over again, the clam will eventually die.
In situations where intentional or even accidental nipping is taking place, the only solution is to remove the clam or remove the nipper. The clam will be an easier catch, as it doesn’t move, but you may find it to be a good opportunity to remove an troublesome fish.