I got 2 stomatella snails, the size of my kids' pinky nail, as hitchhikers... Now I have about 50, the size of his finger. I put 4 tiny ones in the big tank, a couple months ago, and now there's about 20.Get some Trochus Snails and they will breed in your tank more than likely. I started with 10 at home and have at least 30-40 in each of my frag tanks now.