I recently (3 weeks ago) purchased a t.crocea clam. It is about 4 inches long and a peacock blue colour. I am running 2 x 96 w actinics and 2 x 150 w m/h lights on a 75 g. I placed the clam on a flat piece of rock on the substrate. He opens up but not like I have seen them in the store. The attached pic was taken the other night. I wonder if he should be open more....I feed coral plankton and bioplankton twice a week as I only have the one clam and a couple of corals. My water params are great 0 ammonian/trites/trates. calcium is about 400 and ph 8.2 alk is 4.5mm/l? not sure if this is the right measurement of hardness....