Hi bomar, that claim reminds me that "if something sounds too good to be true, then it probably is". I have never heard of earthworm flakes--who makes them and where are you getting them from? I feed my fish as much variety as possible, so I would probably give them a try (I know earthworms are an excellent food source), however, I wouldn't put much stock in that claim that you will get double the amount of fry. Just sounds a little far-fetched.
p.s. that's a fine looking angel in your avatar.