This is probably too late and not really practical, but would a hairdryer help with the goo problem?

I've petitioned Greenland to give us our gulf stream back, but so far, no luck.

A hairdryer might've if I had a hairdryer. I haven't had one for decades. (It occurs to me too late that I DO have a hot pad and we have plenty of extension cords...that thought came just now...)

At the moment, the fix is holding and we have running water again.

Do you think that the horses would figure out to break the ice eventually? Maybe just by trying to knock the thing that's between them and the water out of the way, or do they not think that way? (Not suggesting you experiment, just curious.)

I hope there's no more pipe drama.

Horses will break ice if it's not too thick but in this case the horse trough is too high for a horse to step over and there's not enough room between the side of the trough and the fence that comes down to its top, dividing it in half. They break thin ice with their muzzles; if there's floating ice in the water, they push that out of the way; it's the thick ice and limited space that makes it impossible for them to deal with it in this (and similarly built) troughs.