I've had two 7" male beani, from my experience they are only super aggressive to their own kind and will bloat if stressed. Both my males died of bloat becaues they were being pushed around by a slightly smaller freddy yellow head, i would recommend to put them in a species only tank. I have istlanum and they hate eachother and cannot be kept together unless the pair is ready to breed, I haven't kept them in a community so i won't be able to comment on that till fatjoe gets me a wild pair so i can put my current f? in a community tank. Grammodes are very mean but several members here keep them in a community tank, i believe they will be fine in a large enough tank. As for the tank size you would need to house them all together, i don't know but i will tell you that a 75gal tank would be fine for only one of any of these fish.