my oscar(6inch then) would kill anything i put in the tank. except for my convicts(1.5 - 2inch) which i placed recently.
he did tried to attack and i saw him bit one of the convict the moment i placed them into the tank. so i seperated them for a while with a transparent plastic partition.
after a while, when the convs got the hang of the tank, i took out the partition and they quickly got their territories marked. hehe.
there's 1 night i came back to see a few missing scales on my oscar and teeth(torn skin) marks on 1 of my convs head. hehe, short brawl i guess, no serious injuries. looked like the convs head was in my 'o's mouth for a while.
but anyway, all in all everyone of them are happy living together now.
it was bad enough to have a fierce(but easily spooked) oscar in the tank, now with the 2 convs around, i doubt any other fish can survive if i placed them in there.