How diluted? I've read that vinegar is a natural way to kill mold. And as vinegar will lower the pH of the water, and my tap is 7.25 I have been using apple cider vinegar in the water. But I can only put so much in the mix because I don't want the pH dropping below 6.2, and so far it doesn't seem to be working.green and slimy isn't mold, it's algae and it only grows where it can get light. I bet you have the white and fluffy mold. I had it on my rockwool and I went after it with a little diluted chlorox bleach spray just on the affected parts and it went away.