You say this is your first try at saltwater aquaria keeping. In all honesty, clams are not good for beginners. I believe they need mature, stable tanks. Not to mention they need LOTS of calcium to thrive.
Hi Bill, I currently have 2 clams, and 1 flame scallop in my reef, and as Ice has stated they require very specific water parameters, and lighting. The colorful mantel is of algae that resides within it, and most of its energy comes from the lights. Aside from the calcium, there is a laundry list of additives that go into the water just about every other day. So as Ice said they are no way beginner inverts, but to answer your question, the fish that currently reside with my clams without harassing them are,
Hippo tang or regal tang
6 line wrasse
bi color dottyback
These have so far behaved themselves in my tank but that never guarantees that they will always act the same, just like people, fish have different personalities, likes, and dislikes....