I've had a semi-bare bottom (about 1/2 sand) 14g for about 1 1/2 years. I now have a lovely coating of green algae mixed with some Coralline. Lately I've been considering adding sand back in, mostly for aesthetic reasons, but also so I can add some Nassarius snails as a CUC to replace the Peppermint's which attacked my new acans. My concern is that if I cover the algae it'll screw my tank when it dies off. I suppose I could add a little at a time. Opinions, please.