My first betta terrorised everything in the tank from my poor little cats hiding in the bottom to my swordtails and black mollies.Lucily my store was hapy to take him back, i now have tried another one and he's the softest quietest laziest fish in the tank. he even gets bullied of my guppies some days. the only thing he seems to want to fight with is his reflection in the glass!
My LFS agreed that they are all very individual, roughtly 2 out of 10 will bully, 1 will hide and the rest are a mixture... pretty good odds! *celebrate anyway he's in there with mollies, harlequins loaches cats and guppies and he's happy... I'm happy too as no more babies! ( it was getting hard finding homes for them all!)