I used to feel sorry for my betta and put him in my community, after a week his fins would be torn and eaten. I came up with a solution where I got hold of a pice of rectangular glass. I used this to corner off a section of my 75G SA cichlid tank. My betta loves his new triangular bowl. The glass will hold in place using substrate and a rock. I didn't seal it off, so that there is water flow in and out of the partition through the gaps thus benefits of the filtration system of the 75G. It is like a small tank within a tank.