i bought a clone dome and the rockwool looks designed to sit in water is that true, should i keep water in the bottom tray and keep the rockwool submerged in water, thanks
No. If you're taking cuttings the idea is to let the rockwool dry out a bit between waterings. The dome should stay misted to help the cuttings transpire as they have no roots for feeding. Click the link in my sig for some cloning info
