Usually you can let them go for about 3-4" in a RW hand water setup like that. Longer if you want.

What setup do you plan on using?

If your using a bubbler all you need is a 1'' tap root then adjust water level to its submerged.
The White Snoop Reviewed by The White Snoop on . When to move to Hydro.. Hi, Some help would be appreciated.. I'm a new grower.. and started 5 BigBud seeds in rockwool. Only 1 has come up.. its about .5 inch tall, starting on its 2nd set of leaves but the first set is browing on the tips Rating: 5