SpirulinaIf you need to find another type of pellets, try New Life Spectrum A+ 0.5mm pellets.
I bought 1mm pellets at first, they were too big for my fish lol. Most of my fish are small like cardinal Tetra. They would still eat them though, by holding the pellets in the mouth and the pellets would go in and go out of their mouth for a while to dissolve a little bit before they can eat it. The 0.5mm pellets were just fine, and they can all swallow them whole.
Those NLS pellets are made of whole krill etc. So it is very good high quality stamp food. I've heard good things about them from other fish keepers before I bought them.
I once hatched some brine shrimps for my Neon Rainbowfish fry. It was fun. Even the adult cardinal Tetra in the other tank would go after them.
Doesn't betta eat mostly insects larvae in the wild? They should love bloodworm. Omega One bloodworm are the real thing. They are good for color too. Mosquito larvae are equally nutritious but not as good on the color enhancement. I've bought way too many different fish food than it was necessary lol. Bloodworm alone I got Omega One and San Francisco Bay Brand freeze dried bloodworm, as well as Omege One frozen bloodworm. As for Brind Shrimp, I also got Omega One and Hikari freeze dried, as well as Omega One frozen brine shrimp, and some San Francisco Bay brine shrimp eggs. I was crazy haha...
Even for betta food, I not only bought the Hikari Gold, but also Omega One betta flakes. Neither was ever used because of I haven't bought a betta yet.
On the side note, Hikari freeze dried brine shrimp smells really good! There is also Spirulina in it. It is very attempting to try some myself.