first grow question on timing thanks!

so i have 16 seeds going in the small sized rockwool cubes, they are all 8 days old and starting their second sets of leaves, each has a root poppin out the bottom of the rockwool cube
im going to be using a deep water culture set up im just wondering when i should be moving them into the buckets? i appreciate any help! thanks

as soon as you see the roots, NOW!!!