That Endli in my avatar just got done eating a 4" oscar.
But I have lost a few tankmates to my ornate. He'd eat anything that I thought might of been ok in my tank.
Just have to understand that you will have to growout your tankmates a little longer or not buy anything that you think might be ok. Just make sure they are big enough.
shes in a 40G with a 7-8" arow but they will be going in the new tank once i buy it.
Shes hard to take pictures of, but full of energy these are pics of when i first got her last month, shes grown about an inch. but big things come in small packages as i found out with my new oscar poor thing
Bichirs have very very poor vision and most of the time they nip at fins is because of curiousity of food, as they are very predatory. I don't think its so much as an act of aggression killing your baby oscar, but more as curious for food. Very pretty fish btw.