I know, winter is gone for a while, but, I was wondering if anyone has tried a tub with heating cables, like those that stop outdoor water troughs from freezing up? I have a small 8X6 HFGH. I may put together a hoophouse also. I will need to stop the water from gathering algae with bleach or something. I have looked at greenhouse heaters, and they are pricey. I realize heaters are probably the most consistent way to go. I am considering having a local guy with a backhoe scoop out some soil so I can put some of the greenhouse underground for more heat preservation. I wouldn't know how to procede from the scoop-out of soil though. I can easily get the scoop-out done, with some money of course. Has anyone done this? I have a subterranean basement under my house, that is a constant 57-62 F. There is a little bit of heat in winter, but much is just underground and the temp is moderated by that.