Thanks RyangI keep most of the fish you mentioned in my 180, the venustsus and eye biter will be less aggressive than the fusco from my experience. If anything they will keep the aggression between them and avoid beating up the smaller fish. I personally find my tank very well stocked in terms of aggression and all the adult males show color and no one is particularly beat up. There is a distinct pecking order to keep everyone in control. Here's my list so you can judge how many fish you can put in your 120. I will butcher the spelling Latin names so I will use nicknames.
Malawi trout. ( not showing color yet but he is way to big for a 120.)
Malawi hawk. ( getting really big really quickly so a 120gal might be too small I have both male and female in the big tank and they get along and are a pretty docile fish)
Venustsus ( Is the most domant fish of the tank but mainly chases the red empress)
Fuscotineous ( youngest and smallest fish but the biggest A -hole in the tank)
Eye biter ( male and female and keep to their own except occasionally pick on the little guys)
Red empress. ( him and the OB are always picking at each other but theres never any damage)
V10
2 OB peacocks
Blueberry OB
Eureka red.
Eye biter
Livingstoni
Blue blood dragon.
Fossochromis rostratus ( no color yet)
Star sapphire
tropheus moliro
And various cats
My in my grow out tank I have
Buccochromis notetenia ( male and females)
Morri
After I add those fish I would consider my tank 100 percent full and a alot of my fish are younge. Having some bigger holes for fish to hide in will make a world of a difference in agression for hap and peacock tanks. I'll attach a picture of my tank for that. I would say you could tank about 2/3 to 3/4 of my list and be full depending on how you build up your rocks.
I would stray away from the hawk unless you plan on keeping very few fish. With haps less fish is better for agression and for 100gal you can put a lot of peacocks in there to make room for your hap tank. I've had luck with a fish every 4 gals on peacock tanks as long as you have plenty of rock work.
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The strange thing is I had all these fish in the 125 for months and nearly no aggression.
Then my 100 finished cycle and I started to move some of the peacocks over to prepare the 125 for my wish list. So the stocking got dispersed between the two tanks, instantly I Noticed the aggression level triple in both tank and I lost couple of fish. It started to calm down a little now but still a lot more thanpreviously.
Totally lack of planning.