We're re-building our hoop green house and using wood this time. We have a aquaponics system where we raise fish, pump the fish water into grow beds so the plants and plant media can filter the water, pump that water into a sump and then that water goes to a large rock and sand filter before it's pumped back into the fish tanks.
We're looking for a way to keep the water in the tanks warm in the winter without it costing us an arm and a leg to heat the green house itself. We're going to have about 800 to 1000 gallons of water in the green house tanks, plus have passive solar heat from the ground that'll have a thick layer of gravel in addition to having windows at the proper angle to capture the winter sunlight and heat. We'll also have vents and windows we can open at the peak of the green house to vent moisture and too much hot air when needed on warmer days.
The problem is that if we heat the greenhouse along with using water tank heaters the temps can drop dramatically in the greenhouse and plants and fish don't do well if the temps are too drastic at night, so I was thinking of using heat cables/tapes around the pvc pipes that connect all the water flowing from tanks to plants to sump to filter vs. using in tank water heaters.
We're also hoping for a solution that'll cost less to power and at the same time keep the temps more stable in the green house. All the walls and roofs are being insulated, too.
Does anyone know if heating tapes would work for this or not?