No blood worms would be the worst thing for them, these fish should be fed on a low protein diet with protein count no higher than 38%. The reason is they are prone to Bloat, buns have intestines running 4x them length of their body to extract nutrients from algae, to high of protein can cause irritation to the intestinal walls promoting parasites that lead to Bloat, so stay away from frozen anything and stick with a high quality sinking pellet like New Life Spectrum and nothing else. This will provide them with all the nutrition they need to live happy and healthy lives.