Angie wrote:
My betta won't eat pellets, only flakes.

Do you feed your Betta anything other than flake?
I ask because a varied diet is best for them.
Feeding a quality flake (or pellet..however, if pellet I recommend
Hikari's Betta Bio Gold), for one feeding and then the other feeding a
frozen food such as Brine Shrimp or Bloodworms.
Again, I recommend Hikari brand on the frozen foods. They simply have a
better quality product.
Stay away from too much dried foods, such as a flake or pellet and then
freeze dried Bloodworms. It can cause constipation and a very unhappy
Betta.
Brine shrimp also has a laxative affect, so it's a good "cleaner" food
too. = )
I know my local Petsmart and Petco's sell both the cubed or flat packs
of both frozen foods in the Hikari brand.
If you only have one or a couple fish, go with the flat pack. It's much
easier to break off a tiny chunk and thaw it in some tank water and
then feed accordingly.