Sounds like a game I've played and might throw some light!
I started with African cichlids and love them , so I slowly worked over into keeping planted cichlids tanks and gradually got bold enough to move plants into my 75 and then the 125.
First thought would be to change up the current tanks to avoid the fight as that is certainly a problem due to tank setup and fish choice!
But first some thoughts of what larger tanks do as they have both good and bad points. No "perfect" tanks in my world!!!
Bigger tanks are more stable, so fish tend to live longer as we can do things that would upset a smaller tanks and the bacteria, water temp and all the other parameters are less prone to sudden changes---if we don't do it.
Water changes are one that I feel "require" more/better equipment set up than small as I do not want to do the bucket brigade. So how is the space? Got room for a reserve water supply? That is by far the best thing I did as it is my first choice for any problem that begins to show up. Many ways to go on that, depending on space and how each of us may need to treat water for the tank.
I had hard alkaline water, making African cichlids a natural choice as I am not a fan of fighting my water. So a plastic food grade barrel was a cheap and easy thing to add to the fish room as it was also usable as a place to set small tanks. I simply punched through the wall to get water from a pipe before the softener and added a tap to fill the barrel. Then I let it come to room temp and when doing water changes, I use a plastic tube and pump to run to the other rooms to refill. I also have drains that make it easy to drain old water to the garden outside.
Lots of options to make water changes easy but it does take some thought on what might work best for your setup. I had 13 tanks and "HAD" to but you may only find it something you "WANT"! I like it easy.
A tall stand for viewing in the space I had, meant a small ladder to reach over into the tank for work but otherwise, I found the large tank much the same except somewhat more "acreage" when cleaning glass. I found it very worthwhile as the larger tank gave me lots more options for fish and part of that involves setting the tank correctly for each type.
Which gets around to fish choices! Not all Africans are the same and not all mbuna are the same, so learning to sort more carefully is a key point for my tanks. Pick any animal and you will find there are those who tend to be killers and those who don't. Whether it is fish, dogs, chickens, or people, we have to look closer at each and sort who we want to keep as friends?
I start with this article as I find it has very good, reliable info and I choose my fish with an eye on the potential aggression levels as stated. From there I set the tank and planting to allow for the natural tendencies of the fish. Part of the planning is not planting where they tend to dig and I do not keep the natural born killer sorts that we find so often in the local shops.
I think of tank setting much the same as I choose where I live.
If I set up a tank like a ghetto and stock it with roughnecks, I expect to get a much different neighborhood than if I set a tank with lots of nice green space and fill it with some of the more "respectable" sorts. I DO NOT overcrowd to reduce aggression as that sure doesn't work with any other animal I see---especially humans!