So I am currently housing a 5" Carpintis, 6" Sveni Pike, and a 3" Gold Saum in my 55g. The filtration is good. I change the cartridges in my Penguin 350 every 2-3 weeks, and I do 25% water changes 1-2 times a week. My question is, would it be an ok choice to put another Carpintis that's roughly 3" in my tank? My LFS has one stuffed in with a bunch of Africans and I feel like I'd be doing him some justice to save him. Would there be an aggression issue? My current stock has no real issues with aggression besides the typical chase when food is at hand. I keep them on a rotated diet of bloodworms, earth worms, and ocassionally beefheart. Any input on this?