Nice pickup.
The key for keeping, and breeding beani, for me was to keep the temp down.
Mine bred at between 68-70'F, and the cool temps seemed to hold aggression down. I have also kept them in my pond in Milwaukee, where water temps dip into the 50sF on cool summer nights
They spawned at a very small size, female 3", male slightly larger
I started with 12 from Pleco Pete, they started killing each other when the temps rose into mid 70s in a 150 gal.
The alpha would simple focus on the next lowest in the hierarchy and work until that one was gone, then start on another.
Below, young female in spawning color
male
