Would anti-freeze kill the pump? What about an immersible heater for cups of water (surely with such a large amount it wouldn't get warm enough to damage)

Sorry I'm not more help.

I'm familiar w/koi ponds. i have to ask, do you have a hole in the ice for your fish? do you have a O2 pump for them? (if no to the hole, never strike the ice to break it,,,it will kill the fish. you can pour hot water on it or a pot of hot water to make a hole)

No to car anti freeze! if an animal should drink it, it's toxic.

Terra cotta, ceramic, concrete, and other moisture absorbing materials are prone to cracking when the temperature dips.This happens when water, absorbed into the pot, turns to ice below freezing temperatures. Ceramics that have been fired at high temperatures, however, usually don’t suffer from this, so if you have finely crafted (or DIY!) pots, you should be okay.

https://www.serenityhealth.com/tips-and-advice/winterizing-fountains.html

alcohol for anti freeze:

https://www.quora.com/How-much-alcohol-would-I-need-to-add-to-my-water-fountain-to-keep-it-from-freezing-in-Seattle-this-winter

I suggest that you unplug the pump before it burns out.

Then to keep the fountain thawed, how about a bird bath heater?

I second unplugging the fountain and using a bird bath heater.

Pouring antifreeze anywhere where a cat or other animal can get it is BAD I would also agree a bird bath heater might do the trick and hopefully this is just a weather blip and will soon warm up.

I must have missed where the op has a cat...

Re antifreeze, there is a commercially available non toxic antifreeze, safe for drinking water. The one I am using this winter is called Peak RV Antifreeze. It is not the same as the antifreeze used in an engine.

Sorry Satt, not sure what you mean...Patricia mentioned a cat and I didn't see where the op said she has anything other than koi...which she doesn't keep in her fountain.

Or are you referring to something else?

I will add though to not unplug...it's best to keep the water moving.

I don't have an answer for the fountain, but the pond - If the ice stays for more than a couple of days, you should open up a hole in the ice so the fish can breathe. Best way to do it is to place a pan full of boiling water on the ice to melt it. Don't pour the water on the ice, let the hot pan do the job. Even though they are still swimming, all their carbon monoxide is being trapped under the ice and will eventually kill them. The hole should be as big as the biggest fish.

Right, auntthelma. I didn't answer where there was no question asked. :)

The question was about the fountain.

If the pump can't move water because it's frozen, it will burn out soon. I've seen it happen.

Now back to the question at hand: First of all, turn off or unplug your pump. There's nothing you can do at this point for the urn at this point, except hope. I had a pottery urn I turned into a fountain and sadly, when it froze, it cracked. Hopefully, yours won't. In the future, when you winterize your yard (and whoever thought THAT would be necessary in MS?!?), simply empty the urn and turn it over and store the pump in your shed. Koi always seem to do pretty well.

coopermcboo,,,just curious if you have koi?

Pumps are great for moving water and delaying a water feature from freezing but if it get's cold enough- as mentioned the pump will fail. Best to get a pond de-icer or birdbath heater to prevent the surface from freezing solid and damaging our urn by the expansion of the ice.

Beth H: I don't have koi personally, but a neighbor does. As long as they have room in the bottom of the pond, they go kind of dormant during the winter. Pretty amazing, actually. Plus, I think she has a ventilation hole she keeps clear.

They sell cattle trough heaters at farm and feed stores like Atwoods, Tractor Supply etc, that is what I use in my fish pond. They are not expensive at all and work great. On extremely cold days my fish are huddled up under the heater....just fyi for those of you with fish ponds

Tthose trough heaters work, but they can use a LOT of electricity. Obviously they're useful for a fish pond, which I guess is what you're referring to, but they're a nuclear flyswatter for a little fountain like this.

Around 15-20 years ago, we used to keep pond goldfish (we're way too cheap to buy koi :). We didn't do anything in the winter, though we probably should have. I'd estimate that we lost 1/4 to 1/3 of the fish each winter, but they seemed to make up for it over the summer. :)

I can't find it now, too much other cruft on the web these days, but back then I found a web page describing a neat passive device for keeping pond fish alive through the winter. IIRC it involved a PVC pipe, maybe with another larger pipe around it for insulation, suspended in the water. The pipe had a J bend at the top to keep the snow out. Supposedly it kept air going in all through the winter, with no air compressor or anything of the sort. I never got around to trying it, though.