I have found that single species tanks don't seem to be too aggressive at feeding time. I had a tank of 6 Oscars and they would eat calm and casual and in some kind of pecking order that they determined. I had another tank of tropical groupies and they ate like it was the apocalypse every time the lids where opened. No food in the water yet and they where going to town. I currently have a tank of feeder gold fish and they will frenzy just because someone is walking by the tank.