I keep a haddoni and a gbta in my tank. I used to have them in a 55g, now they are in my 125g. They are rather close to each other too. One foot, if that, is all the is between them. Never noticed anything going on between them. My haddoni is around 18" and the bta is around 5". I only feed mine once or twice a month. Like Toddrtrex said, the more you feed them the faster they grow.