No, have it cover some of the clay pellets, but not the RW.

You test runoff PH with a PH pen. Probably not sure what you mean here.
Opie Yutts Reviewed by Opie Yutts on . flood level and rockwool Is it recommended that the flood level touches the bottom of the rockwool (1" cube inside hydroton) each time I flood? throughout the entire grow. Also, how do I test the runoff PH? not the reservoir. Ebb and Flow system Rating: 5