White Poo!!! please help my Flower horn?

Sounds like you're overfeeding him. You shouldn't be feeding him shrimp everyday, even though flowerhorns are primarily carnivores. You should be feeding him the high quality pellets as a staple diet, but supplement it with protein such as the shrimp and possibly blood worms. I recommend you get frozen or live food instead of the freeze-dried as most of the nutrients has seeped out of it in that state.