I would consider getting a better product than flukers.
Flukers isn't exactly a good gutload.
As far as fresh products, try:
kale, mustard greens, dandelion leaves (even the flower is good), collard greens, and apples.
As far as dry gutload, you can either mix your own (I have the recipee if you want). Or, you can try cricketcrack product.
Perhaps, by upping the quality of the gutload, you will lessened his habit of eating leaves.