Hetertilapia buttikoferi is one of the larger and most aggressive Tilapines. When I had some, they easily hit 15" in a very short time (I have heard of individuals hitting 20" or more), that after killing every other fish in a 150 gal tank. Yes, mine was an impulse buy 30 years ago, before I knew what I was getting myself into. I bought a few, but ended up with 1 in a kiddy pool outside,after a murderous ti-raid.
They are never found in small streams or small bodies of water in Africa, usually only in large, deep rivers, so a tank of 300 gallons or more for 1 or 2 individuals should be thought of as minimum. They have strong vegetarian tendencies, and are great recyclers in nature, and can be found following hippos, eating their dung.