Balas are a real skittish fish, in fact all sharks are jumpers to a point. I lost a nice red tail shark when I was starting out, because of a small opening. This shark was king of the tank
and it still jumped out. I have 2 6 inch balas in my 120, this tank is in my home office. It doesn't bother them when I come in but if the wife or kid comes in they head for the back of the tank. When I got them, they where about 2.5 inches and I had one of them jump out of the container at the fish store when we was bagging them up. I had to catch him before he got on the floor.