i've got a 75 gal malawi tank with 20+ fish and they all do good. just like everyone else said, they dig so watch out. I have sand and there are "craters" all over the bottom of my tank. i run both an emporer 400 and a eheim classic canister which is plenty of filteration. i am probably going to be breaking down my tank soon and will give just about everything but my plecotemus though i'm not sure how long i'll have them. if you decide on malawis you can have some of mine if you don't mind driving.