Everyone I know dosent have a problem with them not being aggressive. But when their babies and you put them with less aggressive fish and don't feed then other fish that in it self makes them less aggressive. Keep them alone untill their big enought to eat fish and feed them you'll be suprised how aggressive they actually are. You can even feed the small babies baby shrimp and baby guppies along with a few very small balls of raw meat. My friend dud this and put then in his 90 gallon community take and they killed his red Texas and hin reg jd but left the Oscar alone lol go figure.