If you use a submersible aquarium heater to keep your watering system from freezing up (or are considering one), please read: I mis-calculated how much water our chickens would use while we were out of town. When I returned, I found the bucket nearly empty and the submersible aquarium heater was still on (very hot!) and had melted one of the suction cups. The device is supposed to turn off when it overheats, but it did not do so. It could very easily turned into a fire. We were very lucky. However, I have also mis-calculated (again!) water usage, but instead used a K&H 250W Stock Tank De-Icer and when the bucket ran dry (or nearly dry), the device simply turned itself off. I tried this (intentionally) several times and it just turned off. Put it back in the water and it starts working again. MUCH SAFER DESIGN. Personally, I will no longer recommend or use the aquarium heater, it's just not safe. So often those disclaimers of "for indoor use only" seem meaningless, but I am taking this one to heart. A little back story on the heaters: I originally purchased the K&H de-icer for use in my 3 gallon bucket with vertical nipples. It kept the nipples unfrozen to about 20F. Since it regularly gets much colder than that here (for weeks at a time), I had to find a better solution. So I purchased a 100W submersible aquarium heater from Petco (petco brand). This solved the problem, at least down to about -5F or so (as cold as it got). However it wastes a lot of electricity, since the lowest setting is 68F. I also got tired of the dribbly vertical nipples. After the near fire tragedy, I switched to using horizontal nipples and back to the K&H de-icer. Works like a charm, at least down to -9F (the coldest I've been able to test). And much safer. I know there are many of you out there who have been using the aquarium heater for years without a problem. That's great. I didn't have a problem either, but it was WAY TOO CLOSE of a call to having a big problem. We could have lost not only our chickens, but our entire house and possibly our lives. If you do use one of the aquarium heaters, be absolutely sure that they NEVER run dry. If you go out of town, make sure you have someone check on it so that you don't run out of water like I did. If you're prone to mis-calculating (like me), just don't use one of these heaters! I for one, am resting much more soundly at night. The cost was about the same. $30 for the aquarium heater or $35 for the de-icer. Note the the Amazon price of the de-icer has always gone down $10-$15 during winter the past 2 years, right now it's the highest I've ever seen it. Free shipping, but wait to order until next fall/winter.