so then could a fish only tank consist of live rocks and sand and fish? wait..hold on... what is the definition of live rocks and sand. as far as i know, they are both lifeless and not in motion! unless i'm wrong. so the fine line between reef tanks and fish only tanks is the corals right? need lots of help from everyone. can i make a fish only tank look like a reef tank with those "fake" corals that the LFS have on their counters?