Hikari Betta BioGold baby pellets and some pellets I obtained from someone named Dean Carstensen in Vermont (he makes them and has growth, complete, and color enhancing varieties). All these pellets, except for the Carstensen growth formula, float for a long time so it is easy to remove uneaten ones. I've tried HBH Betta Bites but they don't float long and nobody seemed really interested in them, ditto that for the Azoo pellets. Sometimes I feed Aquarian pellets and those usually get eaten.
Occaisionally I feed Hikari FD bloodworms but they leave an oily film on the water surface which I have to remove by laying a paper towel on it. I've thought of feeding mosquito larvae in the summer by leaving a bucket of water with a few leaves in it in the back yard but I am leery of diseases.