A 225G would be a great tank for an all male. I have a 220G all male hap/peacock running for almost 4 years. Most of all the fish have been together for at least 2 years. At the moment my tank is pretty calm. I have a 10" venustus that chases a few of his tank mates but he doesn't really try to hurt them just to show he's boss. You can pretty much put any hap/peacock in there but I would suggest trying to put the majority of your stock at the same time as juveniles. Also try to put them close to the same size if you can. If you can find juvenile males that would be best but you may have to raise unsexed fish until they show color and remove the females. If you add peacocks and haps choose ones that do not look similar or they will fight one another. I only have 3 species of peacocks and 17 species of haps. Zimbawe rock, milomo v10, b. rhoadesii, b nototaena, c. rhoadesii, d. kwinge, n. venustus, n. livingstoni, p. tanzania, p. mdoka white lips, rhamphochromis longiceps, stigmatochromis pleurospilus & "spilostichus type", t. nigriventor, o. tetraspilus, champ caeruleus & spilorhynchus. Most of these haps are hard to find but you can put more common haps like electic blue, red empress, and c. borleyi. I wouldn't put a breeding group of p. tanzanias in there unless they were the largest and most dominant in the tank. P. tanzanias are very docile and they won't breed in a all male tank usually. A separate tank would be best for them. You will also probably need a separate time out tank in the future when they mature to house an overly aggressive male. You will always need to be on your toes and watch the tank everyday for aggressive tank mates, but once a pecking order is established it gets a lot calmer. Stay away from n. fusco, they are too aggressive and absolutely no mbunas of any kind.