I got a betta almost a week ago, and have been feeding him one or two pellets once or twice a day. After a couple of days he started eating a pellet or two, but would spit it back out. The last day or two, he simply doesn't eat.
I feed him any of three different types of betta food--Tetra O Betta Min Tropical Medley, Aqueon Betta Food Pellets, or Top Fin Color Enhancing Betta Bits.
I did about a 50% water change the other day, and will do another 50% when I get back to the house. I'll wait a couple more days to do a complete change. I use Top Fin Betta Water Conditioner.
Is it possible that he's too scared to eat? He spends most of his time inside the log I got him from PetSmart. Although I did notice him outside of it when I got up this morning, he darted immediately back inside. Don't know why he'd be afraid of me, hee hee.