Oldfishlady houses almost all of her adults together, I think. She really should come on over and put in her 2 cents, but she's very busy I suppose. And I don't think that aggression, per say, is needed to spawn. My pair (a petco male and a hobbiest bred female with a known family history of gentleness) spawned just fine with very little chasing or fin damage. The female was one of the best mothers I've ever seen, helping to pick up eggs while not eating a single one, and even helping to build the bubble nest. My male was such a good father, I left him with the fry for nearly 3 weeks. The only reason I pulled him was because the shrimp I added as a cleanup crew freaked him out. I now have 75-100 of their 4 week old fry.
Solstice - cellophane HM female