I believe that fish poo and cleaning your filters tells you a lot about the food your feeding. The smell of your filter when you clean it and also the poo tells you how much of the food do they actually digest. Feed your fish Showgun for a while and then Sakura for a while and observe your filters and fish poo with both the foods. You will then notice that there must be a huge difference between the two. Just my opinion
"Legacy of Koi Pride."