I only have a pair of oscellaris, and never had a problem with them. I have them for about 5 years. I wonder if it is because I have neither corals nor anemones, or because of the other fish in the tank, but they do not really pay much attention to any other inhabitants and ignore my hand. At night they sleep on the top right top corner of my aquarium. I am not sure I can call them a mated pair, as they do not spawn, unlike my chromis, so maybe their aggression remains minimal. One is quite bigger than the other though.