I have an Oscar that is prob about 8 inches. Ever since it was big enough I have given him feeder fish once in awhile for a treat. I also would feed him frozen food like bloodworms, beefheart, brine shrimp, ect. As well as his regular everyday diet being hikari pellets. A few months ago he started acting weird and wouldn't eat anything. I did some water changes and put little salt in tank an after couple days he was basically back to normal and started eating the pellets again, which is only thing I fed him for little while after her got better. But now he won't eat the frozen food cubes or live fish. He eats as many pellets as I will throw in there he eats meal worms, crickets, even like a piece of chicken from my dinner or something like that. But no goldfish. It's strange I throw one in there he will stalk it around the tank but won't eat it. I've had one little goldfish in my tank for almost a week now. Eventually he will get sick of him and I'll find it chomped up in tank but not eaten. Any ideas why he won't eat them anymore or what I can do to make him start again? I barely fed him fish but it was fun to once in awhile and now he won't eat any at all. It's almost unbelievable to have this 8 inch fish living In same tank as a little half inch goldfish. And he won't eat the frozen cubes either but will eat anything else I throw In there.