I have just noticed some kind of mold growing on my medium. i dont see it on the plants themselves, only on the top of the medium, and its only happening in one of my grow rooms, the cooler of the two. its a greyish color. so far it doesnt seem to be hurting anything, but i want to get rid of it before it does. what is the best way to get rid of it without hurting my plants? and how do i prevent it from coming back? the ventilation is pretty decent already and the temp at the floor stays at about 65-75 degrees day and night. thanx for any help you guys can give me.

I already add a little peroxide to the nutrient solution about every other time i water, about one or two teaspoons per gallon. i have plants that are at the beginning of their flowering stage so i really dont want this stuff to spread. do you think pointing a couple of cfls under the canopy could help?