I have lake snails that will stir up my sand, and also had monster FW clams that trash my tank by rearranging my nicely placed fake plants and driftwood. But even tiny fingernail clams will do it. I currently only have one deformed clam in my 55 along with my horde of snails, and they do OK, but I still have to stir it up. But they keep my sand from going stagnant. Just avoid ghost shrimp or crays until your baby is big enough to eat them, otherwise they'll get him first.