ive heard that pellets arent a good diet for bettas. I only give my bettas flake food and freez dried bloodworms. They seem to like it better than pellets anyway. Ive also heard that bettas have taste buds and will not eat some foods because of how the food tastes. Try some flake food instead.
i usually leave my filter on all the time unless im trying to breed.(still havent gotten it right though.) It hasnt botherd my bettas wen there in there and its on. They seem the same to me wether i have it on or off,but it may be different for your fish. If you think it bothers him id sujest try wat Sicklid said.(I have 4 bettas by the way just in case your wonderin)
hope i helped
