This is more anecdotal, probably untrue but sadly amusing. Most of my fish, all cichlids, from the first few I brought in are now in color, and for the most part, doing well. My fish are a mix, same region, different lakes. When I set up the aquarium, I made sure to get only one of a species, hoping to cut down on aggression, and it has worked well, save one incident.

Apparently, when I made this plan, I failed to take into consideration that not only were cichlids more aggressive towards same species, but also towards fish of similar color. (Unlike the human species who often seem more bothered by differences than similarities. Fortunately, this only effected my Demasoni and Yellow top. Both came in originally from the same breeder, and both were under half an inch when they first arrived. For over a year, the Demasoni was fine with everyone but the yellow top. That one, the Demasoni would actually hunt for and instigate problems. Most of the time, there were enough caves and rocks and the Yellow top was really good and maneuvering at top speed. With one minor fin nip, the Yellow top was never hurt, but I did worry about the stress he was under, and removed him to a seperate tank a couple of times for a week, which, once he was returned to the main tank, calmed him for several weeks.

About a month ago, the Demasoni was at it again, chasing the poor litter bugger all over the tank up until lights out. The next morning, I couldn't find the Demasoni in the tank. Oddly, the Yellow top was chasing every other fish in the tank. Late afternoon, I removed all the caves and rocks, because the fish tend to begin decomposing immediately, losing all the scales and turning into an unrecognizable lump of whatever in a matter of hours. Way in the back, I found the Demasoni. He was alive, but missing his entire tail fin. Despite the fact that the rest of the fish were sprinting around, trying to find somewhere to hide from the big bad human hand, the d... Yellow top spotted the Demasoni and took up chase.

To make a long story short(er), the Demasoni recovered and grew back the entire tail, then promptly died. My Yellow Top had a psychotic break. Seriously. Changing places in the pecking order over a period of time is one thing, but this happened overnight. 99% of any 24 hour period I spend in my room, in the dark except for the tank lights. Complex pain thing, which thanks to our government's decision that since addicts should have opioid medications, neither should anyone else. Never mind having what was adequate pain control for the past 16 years. Anyway, point being, I see them all day, and there was no change in anyone else's behavior prior to that day. I considered that perhaps my Red Zebra might have bitten the tail off followed by the Yellow top taking advantage of the situation to beat down the Demasoni, but the other wish had never taken much interest in each other as far as aggression goes. Even if the amputated tail fin was done by one of the others, the Yellow top the THE low man in the tank. Now, he chases the others who are all larger than he is.

This is like the old Mad Magazine add with the bully kicking sand in the 95 lbs weakling who then buys a weight lifting set and kicks the bully's butt. The fact that an injury and death occurred makes it more of a tragedy than a comedy, or maybe a comic tragedy. Anywho, I don't have the answer except the psychotic break, but thought I'd share.