Well you might have a problem now since you gave him blood worms he will refuse any other food. I just had new betta that i bought for my friend and could not give it to her because of that problem. He ate form day 3 that i had him and i decided to give him blood worms , since he tried that he refused the other food. So it took me 10 days until he finally ate the pellets. So if you going to have this problem you will need to be patient because its very annoying, and do not give him any blood worms until he eats real food.
Flakes is not the best choice at all though, however i tempt my new fish with the flakes before he ate the pellets. Flakes can cause constipation in the future. So if you can go to the store and try to find
And its good that you don't have any gravel in his tank because it will be easier to monitor if he ate the food. New betta that i have was taking the pellets in the mouth and spiting it, then after its sink to the bottom he was going after that and eat it. And actually just yesterday he ate first pellet, made me happy.
I kind of thinking you going to have the same problem. Blood worms also can be constipating and people recommending to feed it as snack about 2-3 times a week. Along its not enough nutrients in it so you will need to get pellets any way.
NewLifeSpectrum are not floating pellets, Omega one are floating. I give one kind to my bettas in the morning and the other at evening.