I'm looking for suggestions on what will be the best clean up crew for my 20g nano. I've acquired a few crabs that have made their way into my tank by hitchhiking on some coral, but that's all I have in there right now when it comes to clean up crews. I've heard from several sources that Nassarius snails are a good choice, but thought I'd get some more suggestions before I get anything. I'm not looking for any one type of invert, so I'm open to all suggestions! What have you found is the best clean up crew for your tank?