Frankly I don't care what they eat as long as they EAT!
The plakat wouldn't touch betta pellets, he liked only the sinking wafers I got for the cory. He ate them off the bottom. I spent a lot buying some sinking pellets for carnivores but the plakat didn't touch them
Then I added neons to the tank and started feeding them Hikari Micro Pellets and the plakat LOVES them and eats them off the surface. He ignores all sinking pellets now.
The delta tail is eating Tetra Betta Pellets because I got them for free. Apparently they are not the best but I will stick to that as long as he likes them.