when to put seedlings in a dwc system

i have a real newbie question concerning dwc system. when should you put seedlings into a dwc system?

one's you have good roots

thanks for the help. i heard that you could do it as soon as the tap root comes thru, also that u could germinate in the system and continue thru ur entire grow from there. u get so much help from ppl on but how do u distinguish fact from crap? im a experiment with a new seedling and drop it in system soon as taproot comes out of the cube and see what happens.