I have, 9 hermit crabs, 3 turbo snails, and 3 sand sifting snails, is that enough to clean the sand? I thought even with them I was suppose to stir the sand. Any recommendations on which snails and how many I need for a 40 gallon tank that's been up and running for three months now? I only have 2 clown fish in this tank. Thx for everything!!