i'm not using rockwool, i just cut some of those stryofoam children letters, stuck the branch inside a slit i made and let it dangle through the whole i cut in the topi have the rubbermade 10 gal tubs. as long as the water is high enough that the breaking bubbles get the bottom of the baskets pretty wet you should be fine for a cloner.the moisture will travel throught the clay and keep the rockwool moist enough until roots break through. if you were to keep growing in it, you could eventually start lowering the water level a little bit once the roots came through and were established