"Cleaner clams" are a great idea, EXCEPT, they don't have a great track record in captivity, and they usually burrow into the substrate and die there unbeknownst to the aquarist, and then their tank spikes...no bueno for the fish, coral, etc.
They are also generally collected in cooler water, and tropical temps likely speed their demise. I'd leave them out of your tank if I were you, esp. since two small clams won't make any positive contribution to most setups (unless the tank is very small).
JMHO/JME