@Ted Brown I wish I could help, I've valued some of your contributions to BYC, but I just don't have experience with the sorts of cold the rest of the nation suffers. I use the huge polytotes, they are what, 275 gallon? That's a lot of thermal mass to freeze, but it doesn't help with the nipples/cups attached. If I had real cold, I'd submerge a heater into the polytote, and wrap my PVC with the heat tape they use to keep RV pipes from splitting - but it seems an expensive solution.