This is the game we all play by keeping cichlids. I read somewhere 'musical tanks' because you're constantly taking out the ones who are taking an extra beating or the aggressors getting a time out and decorations rearranged. Like Stanz said, you can never predict the outcome with cichlids. If you read about keeping african cichlids, they purposely overstock their tank such that there's no room for any single fish to set up territories. This works with CA / SA cichlids also however, these fish get much larger than most Africans so tank space becomes an issue.
I just ran those three fish into aqadvisor to get a ballpark, they didn't have a 250 only a 240g but either way you're sitting at 37% stock. You could comfortably add more fish, but having two big monsters would probably produce duels. Here is an example of what you can do. Now remember aqadvisor is a framework and gives you the 'ball park' idea of whats in your tank but should NOT be considered unbreakable law.
1 Red Terror
1 Green Terror
1 Jack Demp
1 Severum
1 Texas
1 Jurupari Eartheater
That leaves you at Your aquarium stocking level is 64%
So just a little over half filled. Which would leave some empty space and empty space == territory to claim and at the end of the day the Red Terror would definitely dominate those areas.
The end state is you'd be playing with fire. Do some research, if you like new world cichlids it might be worth dropping the Red Terror and doing a very healthy mix of fish in a 250g. Or keeping a red terror as a solo in a smaller tank like a 180. Look up some videos and read, read, read.
**Just a warning here I've only been in the hobby for a little over a year now but I read tons and have my own tank to go off of.
**Also, I'll mention it again, there are no guarantees with cichlids. I had a angelfish go berserk and kill all of his tankmates one night. I'm talking murder. Gourami's ripped in half. Decaptitated swordtails. He was the ONLY angel in the tank. You never know man, you never know.
