Go to your local garden center and buy some fungicide. I found the white fungus among us growing on my rockwool cubes one day, mixed up a spray bottle of fungicide, sprayed...no more mold! It was gone in less than an hour. I had "Daconil" fungicide concentrate on hand that I bought at Walmart last summer for some flowers I grow in the shade. When I first discovered the mold on the cubes I sprayed them, the plants, and all the surfaces too. I added another fan, kept the door open, sprayed everything again about a week later, and now I just spray the grow medium once a week or so.