Well, I installed a 55 gal drum solid filter into my system last night. Have a lot of green slime on the roots of my DWC plants. I have decided to not attempt to heat the water or greenhouse this winter if possible. I did however build a simple black poly solar collector. Had it installed outside the greenhouse and was getting considerable heat collection from it. Have moved it inside the plastic to attempt to insulate it from the air temp outside but still collect IR heat. Will let you know how it works. Never would have thought this would become so addictive.