I have a 12g nano that crashed and now I'm rebuilding it. I had a bad cyano and red hairy algae outbreak that I treated with chemiclean then a rock scrub and lights out. Parameters are all great now but rocks are dirty. I bought 6 turbo snails and 6 hermit crabs today and acclimated them. They don't seem to be eating the detritus. Can anyone explain this?