That is weird about the lemon peel and the derasa. I have a hippo and a lemon peel with my derasa and neither one of them bother the clam. I say the spinach helps (my fish even the clowns and my cleaner shrimp LOVE spinach).
I had to remove my lemonpeel a while back he loved terrorizing zoas. My flame doesnt touch anything though including clams.
Great additions Meowzer! I've always thought about some blue reef chromis