Hello, I have a floating raft system with hydroton in net pots.  Since I started the system about five weeks ago, I have had mold developing (at least I'm pretty sure it's mold) on the top layer of hydration in the net pots.     I went to a local hydroponic store and they thought the problem may be related to light hitting the top layer of hydroton, or low DO levels, so I purchased some covers fo…