Mine isn't aggressive really, more of a show off when he feels like being a bully. Normally jumping all over the tank will his gills flared and fins up. He may try to eat the Congo tetras though.
I would not consider this species docile, but like most cichlids individual behavior and/or aggression levels will vary. The fact that it is by nature an open water predator, should be self explanatory as to how peaceful it will be with smaller fish. lol
Gotta agree with that. D.comps are one of my favorite species to keep. I had one a few years ago that was about 6" and he was quite a jerk always chasing anyone that came near his end of the tank. Then the one I had the past two years (recently lost him, just got old) was an absolute monster in size at an easy 11" and maybe even closer to 12" and extremely thick/tall body....yet he was a big softy and didn't bother anyone at all. With that said, I'd say tetra would for sure be in danger at some point no matter what. Hard to suppress that natural instinct when a small bite size fish swims across your nose.