I have a silver dollar and an opaline gourami. I've seen the silver dollar eat the gourami's poop... is that normal or is there something wrong? I'm starting to think maybe they aren't such great tank mates. The silver dollar seems to be schooling with the gourami...? I was thinking about getting another fish for the silver dollar to hang with but I'm worried about tank size and really don't have the money to upgrade to a larger tank. I know I'm probably pushing it with a 20G tank anyway. Help?