My Betta Fish hardly eats. Please help?

I feed him once when I go to sleep, and once when I wake up. Whenever I give four or five pellets, he puts it in his mouth, but just nibbles it then spits it out. He only does that with maybe two or three of the pellets. Then he leaves the rest, so I have to take it out. He isn't eating that much. What should I do?
 
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