I wait until the fry are a coupla weeks old or so before transferring 'em. For one thing, I never seem to be gentle enough with the fry until they're a few weeks old, and end up losing a fair number (fair number = most). Waitin' lets them build a little size and strength. For another, nearly as soon as the fry are gone, the male will wanna mate again. Leavin' the fry with the parents gives the female a bit of a reprieve from that and a bit of extra time to recover.
WYite