The little guy is acclimating right now. I can't believe how small he is, his arm span is only 2"-2.5". I have a couple hermits and a hitchhicker crab in the tank with him now but I am worried the crabs might be too big for him. The hitchhicker crab's shell is about 3/4" wide, is this too big for the little octo? Would small ghost shrimp be a better size for him?