Ariel ate her poop when she was younger too. We tried so many things -- we gave her pineapple, put tobasco on the poop (not a pretty sight and it smells horrible
!!!), and added some type of powder that the vet gave us to put on her food. None of them worked for us. What did work was the Solid Gold S.E.P. I sprinkled a small amount to her food everyday and she gradually stopped her nasty habit.
But before you start adding anything to his food, I'd suggest keeping a close eye on him. Every time you catch him in the act of eating his poop, make sure he knows that you're not pleased with his habit.