In my opinion all depends on one or all of the following: 1. The species of fish. 2. The foods being fed. 3. Water conditions. 4. Lighting. This is only an opinion. I'm not an expert. Ed Join the AKA at http://aka.org/modules/tinycontent0/index.php?id=9 Archives are at http://fins.actwin.com/killietalk/ Modify your subscription at http://www.actwin.com/mailman/listinfo.cgi/killietalk