I have at least 12 nassarius snails in my 120 and they do come out mostly when I feed the tank but noticed they come out at night or early morning too. They do a good job of breaking up my sand but I love the diamond goby best of all for that job. They can jump initially, re-engineer the sand around each rock, and spit sand all over so you can't put a lot of corals directly on the sand sometimes but it keeps my sand clean looking all over!