I know amphipods are good overall, but I have too many and they are causing problems with my zoas. For example, I have a frag with 3 heads on it and a dozen amphipods. I blow them off with a turkey baster and they come right back. The zoas are staying closed a lot as a result. It's a 13 gal. tank with no fish and I would like the smallest animal that will control them. I have seen shrimp, wrasses, etc. mentioned, but what is the smallest? Thanks