When I am just starting clones and have no roots I use a flood and drain with air stones filling the water to the bottom of the rockwool enough roots are exposed through the net pot. I use the 6" net pots in 3 gal buckets, the rockwool is 1/2" from even with the top. Once the roots are established I lower the water level till it is ~1" below the net pot. Once I move them to the flowering station (5 gal buckets), the water is ~7" in the bucket which I think leaves 2-3" between the pot and water. Both systems use a pondmaster pump that puts out a lot of air. I dont know if this is the best, but I have had good results with this system. My yeilds have been pretty good with some very large nugs, some nugs are as big as 90g wet 21g dry. I usually see about 2oz a plant in a relative small space (3'x5'), I am looking to expand my room and add another 600 digital for a total of 1800.