My 2 cents worth.......I have a 55 with 4 acei(3 males 1 female) 3 yellow labs (2 males 1 female), 1 male red zebra, 1 male sunburst peacock, 1 female saulosi (if anyone has more of the saulosi, PLEASE let me know, she's lonely) and a 5 or 6 inch pleco. I know that my ratios are backwards, but it's just how it's ended up after 3 years, and the tank is running well. None of the females are stressed, and the only fish that shows any aggression is the zebra. I find the mildest fish to be the acei. I've stopped saving fry because I just have no more room, and I can't be sure of mixes.