I really think it was the Male ray in that tank. He is starting to get the the point he is mature and I am betting it was him. My Aro is big, but not that big to take out a 6"+ bala shark. The Bala was fat, have had them for some time now. Sucks but thats the fish world. Im just surprised the ray even got ahold of him. Bala's are fast, and they usually stayed away from the ray, but then again, rays are good at catching live food. Wife was not happy, she said the Bala's were her second fav. fish in that tank. Rays being the first of course... Why, I have no idea, Id rather see the Aro or the CK more than the Bala's. But we did have them for awhile. O'well, like I said, thats the life of a fish keeper..