I have a fairly large emerald crab and it has lost a lot of his color. And has been this way for over a month. Looks kind of chalky. there is not much algae for it to eat at all so last night I rubber banded some romaine to a piece of rubble and placed a large piece of cheato in the tank. When I got up for work the romaine was gone and he was working on the cheato. I never knew anything really ate cheato. Do I need to feed it more romaine?