Well just bloodworms isn't...I believe a balanced diet is necessary. Just like with us we can't just eat vegies or we lack protein etc... so i believe you can feed flakes, bloodworm, frozen brine shrimp all at diferent times of day and give them treats everynow and then
My guppies dont even get bloodworms and i've already had 2 sets of fry. I feed mine a variety: flakes, crumbs of algae discs(weird but they love them), brine shrimp pellets , and tubifex worms. I even use the same on the fry(except the disc and pellets).