I have one male and four female siamese fighters in a four foot tank with two angels, two golden gouramis, two blue gouramis, 4 butterfly rams, 8 serpae tetras, one bristlenose and two ottos.
And I don't have any probs. I think cos of the tank size and that I have lots of plants for fish to hide each species seems to stick to its own. Every now and then someone will get chased a bit or nipped a little, but I think this would be normal in any tank, mostly they live in harmony.
Everyone has different experiences though, I've heard various things about serpae tetras getting nasty and angels being dominant, but it would depend on the circumstances I think.
all the best with your fighter if you get one, they are a beautiful fish and I have found most of them will come out to see you. I used to have one that I used to stroke on the back once, very friendly.