I bought a dempsey yesterday and put it with oscars they are all the same size so the lady said they should be fine. Well at fist they were then little jack started to nip at my oscars so i took him out overnight. This morning before work I put him back he is just staying under the rock which is better then them fighting my tank is 100 gallons wich zI was told was too small but my oscars are 2.5 inches at the most so for a year they should be good and If i feel they are getting to big ill buy a bigger tank - money is no option for Eminem - Pumpkin - BabyGirl - and Joe-(GI) he is black with green and orange. I also noticed yesterday the "albino" Eminem hes not pure white and he has black was spending all his time with babygirl at the one side of the tank while Joe and Pumpkin were at the other. Shouldnt they be way to young to start pairing up? Any suggestions/help is as always appreciated.

Some people keep Jack Dempsey's and Oscars together and have no problems, other times aggression rears its ugly head. It's either going to go one way or another. Obviously the larger tank you have, the better it will be because the fish wouldn't be crammed together all the time. I think it would be up to you to decide whether there is too much aggression when the Jack Dempsey is in with the Oscars.

Regarding the Oscars pairing off, I'm afraid you've got a very long wait. Contrary to what some people say, Oscars do not pair off at a very young age. Yes they hang around with each other but you will not know you have a proper breeding pair until they hit maturity and start laying eggs. If you had a batch of six and you did notice that two were hanging around with each other, you could take the chance and remove those two and hope for the best, but it wouldn't be conclusive evidence I'm afraid.