Just did a quick search for one brand. Petsmart seems to be a good site for detailed food info.
HBH Betta Bites
Nutrient-packed, color-enhancing fish food for Bettas. The micro-pellet diet improves Betta health, growth, and coloration.
Fish meal, wheat flour, soy flour, fish oil, brewers dried yeast, squid meal, soy lecithin, krill meal, l-ascorbic acid phosphate (source of vitamin C), choline chloride, vitamin E supplement, niacin supplement, astaxanthin, d-calcium pantothenate, riboflavin supplement, thiamine mononitrate, biotin, pyridoxine hydrochloride, folic acid, vitamin A supplement, vitamin D3 supplement, vitamin B12 supplement, manganese sulfate, zinc sulfate, ferrous sulfate, copper sulfate, sodium selenite, potassium iodate, ethoxyquin (preservative), propionic acid (preservative), red 40.
- Crude protein (min.) 45%
- Crude Fat (min.) 11%
- Crude Fiber (max.) 2%
- Moisture (max.) 8%
- Ash (max.) 12%