I had it covered the whole time. Anyway, I used diluted Bleach, and sprayed the lower stem (effected area) and the rockwool, including surrounding surface. I alos sent 7-8 sprays into the resovoir and I know one spray directly hit the rooted rockwool where mold was also found. I then wiped and patted the grow surface near the stem after giving it a minute so the bleach would't do too much to the point it would too cause damage but yet defintely killed all bacteria.