My gulper eats everything but the food I give him. Hes only about 8" but he has eaten 6" Sevrum, 6" snakehead (super mad about that), 2 bichir's, 6" sliveer aro and more. But if I hold shrimp or dead comets in front of him he wont eat. If I just drop food in still nothing. Should I just start buying him like 4-6" cheap fish to eat???? Help please