What do you feed the fish in the tank? If you feed frozen food, you could probly get away with not feeding your clam at all. I have had my Dersa for about 3 months and havnt fed it once, and it looks great. It even grew. I can risk feeding it because it would be adding unwated nutrients which Im trying to get rid of at the moment. My tank is a seahorse tank so I have to feed frozen any way.