So at what point do I start to think that this is more than just acclimation issues? I got the clam on Saturday and it seemed to fully extend it's mantle (as seen in the picture).
Sunday seemed less so but it was tank cleaning day so it's entirely possible that it was just irritated, plus I really didn't pay much attention to it until last night when the lights.
Today I've fussed with him and moved him around a lot and he continues to look like the first picture I posted.
How long should I wait before thinking that this might be PM (or something else) and give him a freshwater dip, etc...? A few more days? A week?