I have a 75 gallon aquarium and I have 15 mbuna cichlids. 5-cobalt blue, 6-yellow labs, and 4-rusties. I'm not sure of the ratio of m/f for the labs and rusties; but the cobalts are 1 male to 5-females. The tank is usually relatively calm but my male cobalt has been getting a little feisty with all the other fish. I rearranged the rocks today during my weekly PWC and things have calmed down for the moment. I thought 15 would be appropriate. With the rocks and substrate I calculated having approximately 63 gallons of water using a formula I found on the web. Is my stocking level considered understocked for a 75gallon? If so, how many would be appropriate to spread out the aggression? They are eating 1/2 teaspoon of food within 2 minutes. Would this be considered under feeding which may be causing more aggression?