Hi Will,
My 125 gallon all male tank currently contains ..........
1 - Copadichromis borleyi (Kadango)
1 - Champsochromis caeruleus
1 - Fossorochromis rostratus
1 - Stigmatochromis modestus
1 - Buccochromis cf. spectabilis
1 - Copadichromis azureus
1 - Protomelas sp. "Steveni Taiwan" (Taiwan Reef)
1 - Sciaenochromis fryeri
2 - Placidochromis sp. "Phenochilus Tanzania"
1 - Crytocara moorii
1 - Aulonocara jacobfreibergi "Otter Point"
1 - Aulonocara "German Red"
2 - Labidochromis caeruleus "Electric yellow"
All of the males in my tank are generally showing full color. It's a delicate balance for sure, and you need to be prepared to add &/or subtract as sometimes some males will become hyper dominant & have to be removed, or are too sub dominant to fully color up in the presence of other more dominant fish. With the exception of my Champsochromis & Buccochromis, all of my fish are adults, and even at a mere 5" the Buccochromis is already solid blue. Certainly some male fish will exhibit heightened coloration when actually spawning, but in an all male hap tank all of the males are constantly attempting to psych each other out, and are generally always displaying & showing good color. In some cases multiple males of the same genus or species will all show good color, but typically one will dominate the rest, and exhibit the best color in the group.
That sounds really nice, The only problem with that is the fact that this would most likely be my only tank with considerable size, so subtracting fish would be difficult. Also, i'd prefer to do a group of all the same species, would this be better to do a breeding group? you say one will dominate the rest, but will the rest still exhibit relatively good color?
Below is a rostratus that grew up in an all male tank. (not my fish, but it will give you a good idea of what one can expect to see) But yes, they are not exactly a predatory species, if that's what you are going after.
I would prefer they be predatory, but the color that the fosso's have surely makes up for their nonpredatory habits. That is a gorgeous fish. Their "eartheater" habits seem pretty interesting and it seems they would be all over the top and bottom of the tank, which is good. 
That fish resides in the tank shown in the link below. You can see how John's tank tranformed over time, and when you get to the last pic you can see how that rostratus was in full color, and approx 10-12" in that photo. Also, the fusco was fully colored up, as were all 4 male venustus. That was in a 125, but I believe he later moved everything into a 180.
http://www.ida-may.com/other/johntank1.jpg
That tank looks amazing, I think it looks better as it progressed and there were fewer, but larger fish. The fact that all the male venestus were colored up is reassuring, as i would like to have all one species preferably.
As those fish grew out, the dom male venustus in that group looked like this,
http://www.ida-may.com/other/venustus13.jpg which is full blown spawning coloration. The other 3 venustus kept their spots, but still had superb color.
In a 180 gallon??? Keep a tight seal on the lid (with no open spaces) and you shouldn't have any problems. Yes champs are fast & powerful swimmers, but they tend to max out at 12-13" in an aquarium, not the 16" you read on various online profiles. If a 30+" arowana can be kept in a 240 gallon, a 12" champ can certainly be kept in a 180, or for that matter, a 125.
Yes, they recommended against them. So they only get 12-13"? That sounds better than the 18" i have seen on some sites, but i don't really like their color as much as i like B. Rhoadesi (sp?) or the Fosso's.
IME start with young males, just big enough that you can determine that the fish are indeed males, and let them grow out together. Keep the tank fairly well stocked at this point to help spead the aggression. Young male fish are like most other young males, they have raging hormones & will fight at the drop of a hat. Unless you see any serious aggression, or obvious signs of certain fish that just won't get along with anything, let them establish their own pecking order. Also keep in mind that as these fish mature they will generally settle down, and pick their battles more carefully. Some of the larger haps can take 2-4 yrs to become fully mature & show their true potential.
You need to have patience, but IMO the end result is worth wait.
Okay, i hope that do mellow out as they get larger, because what i imagine is a nice looking, active "shoal" of sorts where everyone gets along. But I would prefer for it not to be too "well-stocked" because i don't really like the look, but i suppose i could sell some off as they matured and mellowed out.
HTH
they look amazing.
