Bought his cool little used NFT style aeroponics setup for $40. The submersible pump sprays water down 2 tubes, one for each channel, which are lined with aeroponic sprayers. Gravity feeds the water back down the channels, through 2 slits in the bottom of them, and into the reservoir through 2 big holes. Does anybody have any ideas for shielding these holes from light? I'm afraid using it in the greenhouse, like I intend, is going to result in ton of algae growth, not to mention physical debris which can blow down them....