How long do I keep seedlings in the dark?

[Paranorman]

5 day old clones

I just linked to this in another thread and realized I may not be clear, I keep about a quarter inch of the rapid Rooter in water, I keep a liquid rooting solution always in my tray, the rapid rooters are always in water (I don’t bother with an air stone in tray, it doesn’t need it)…sorry if I wasnt clear before