Tango finds the sinking pellets too. Bettas are SMART. Tango watched the cories eat their pellets and learned very quickly that there was food on the floor. Now he hunts for it all day. And he got so fat and sick that I had to find a way to stop him.
I put him in a breeder box when feeding. It's vented on the sides and it floats in the tank so he's in his tank water. No stress for him because I feed him in the box and he looks forward to it. I use Lee's three way breeder. If you take the bottom grate out and the middle divider, it works GREAT. It's pretty big.