Yeah as is say my Severum is surprisingly aggressive and he went in the tank the same time as my 3 spot gourami and they were fine, it was just every time I introduced other largish fish he went for them just sort of asserting his authority as its his tank. The Angel went in and as it was an adult the Sev hated it and went for him till he was weak then all the other fish joined in. I desperatly tried to get my 12gall heated up to move him but it was too late. After that I introduced an Oscar and the Sev got nasty again so I but the Sev in the 12gall for a couple of days (a sort of solitary confinement) so the oscar could get settled in, afterall new fish already have the stress of the move to deal with, I then reintroduced the sev and all was fine, still gives him a bit of a chase but the sev sticks up for himself a bit more. The only problem that can happen is the dominant fish in the tank in your case the Con will grow very fast to show whos boss and at the same time it can strangly make the other fish grow slowly or curb their groth entirley. I have since bought a young angel and he hasent grom since I bought him several months ago!
