If you mean Herotilapia buttikoferi, they grow very quickly,
Mine hit 12-15" in a little over a year, and went on to 20" + another year later.
Mine outgrew a 150 gal tank after about a year, and needed to be moved to a 300 gal Rubbermaid.
By the time they hit about 12" they killed all other fish in the tank, and started in on each other.
In the 300 the aggression chilled a bit, but I have always found them to be one of the most aggressive cichlids.