I had been growing copopods in a ten gallon tank, had a bunch of hermit crabs in there (took the crabs out of the big tank as they were coral munching). Anyway, I decided that a 30 would be better for this project and did some tank arranging. Yesterday, I added a bag of caribsea's Seaflor, made out of a bunch of pooka shells. This morning, almost all of the little crabs had changed shells to the ones just put in. Did they do this to blend in? OR would there be some other reason, like the mineral content.