i am sorry to bring in the bad news, but I personally wouldnt put any "Aggressive" fish in anything under a 55 gallon. this is for a lot of reasons, aggressive fish need territory and a 30gallon wont do it for space, they are messy eaters and when all their food goes on the substrate it will make the amonia rise a lot(but if the tank is bigger, that wont factor in as much). i would go with either a 55 but the best would be a 75. and also chose your fish wise, and let us know what you want to do.