The books have said this about angelfish and goldfish fry.

I agree that keeping fry in a large tank, good water and good food they'll grow big fast. As long as these needs are met it seems like the fish should grow day and night (my fry have grown to 1 1/4 inch in four weeks with the lights off at night). But for some reason some books say that the fry will grow faster if the light are on 24/7. But they don't say why?