When I was at the beach I found a bunch of moonsnail (http://4.bp.blogspot.com/_9jTkGowIIL...g280409p09.JPG
) shells. They have amazing colors, but not really unless they're wet. Then I had a great idea-maybe I could put them in my tank(s). If I made sure they were safe (vinegar test??) and cleaned them really well, would they be okay or would they harm my fish? None of them are big enough for a betta to fit into, and if they were small enough for a betta to get stuck in I could close the hole. They are all smooth, with no sharp edges, so that wouldn't be a problem either. So any opinions/advice?