Cubans that I have had kept would rip apart a equal or larger fish, My male would attempt to kill anything, but fish that pose no threat, but same size or bigger? it was on. My Grammodes was incredibly fast, using the speed zones in attack mode, but was smart enuff to stay the hell out of the Cubans way. Size Matters, but this is not the UFC, Just use that rule/suggestion if you keep the 2. But don't discount a Cuban, Grammys are Psycho, but they are also very, very smart, if they feel they can not dominate, they will keep their distance. IMHO
My male (8") killed a breeding male Mota (11"+), with so much speed, my buddy did not even notice it in time. Sad really.