Whats wrong with my Clams?

[Ginu]

I dont know much about clams bessides the i really want one, however 20% water changes daily would be difficult to manage for a system that size...

Any chance you can divulge the secret with the clams? I want to get one and currently have a cleaner wrasse in a 34g cube, so now I'm afraid the wrasse will nip at a clam if I were to purchase one and they are pricey 60$...