I'm more worried about them freezing and then leaking. I was browsing an on-line retalier this weekend (can't remember which one) and noticed a note advising customers to ship 2-day air or better if ordering anything liquid due to temperature concerns. I hadn't thought about that before other than w/ livestock (and had a box of frags several years back freeze after the FedEx truck turned over on the interstate in January). I'm running low on Alk, but can probably make it a while longer. The last few years, I've gotten a lot better about keeping "extras" on hand (like impellers for pumps/skimmer pumps; bulbs, etc), which could be a topic for a separate thread: "what do you keep on hand in terms of spare equipment, parts, and so forth?" There are times I think I could open my own store....