I really like having multiple water sources when possible. It is an insurance policy against leaks, grossness in the water, and being unable to get out to the animals to give them water in case of emergency.
My horses have a 300 gallon rubbermaid tank in the paddock. I keep goldfish in it to manage the algae. The horses seem perfectly happy to drink out of it. I don’t change this water often, just keep it topped up. In the stalls there is a bucket for each horse. The bucket is easy to keep scrubbed and clean.
I’ve seen the horses preferentially choose fish water to the clean buckets, and I also see sometimes them preferentially choosing the buckets more than usual. When the latter happens, I check out the tank to see if all is well, and I may spill some water out the top to refresh it.
I put in the tank originally because we were out and about for the day and got home later than planned. I had two buckets per horse but it was a hot day and I was extremely concerned that they wouldn’t have enough. However, since then the tank has saved my bacon a few times, through power outages, fire evacuations, or worse, both. I had to leave the property with the two older horses still on it and could not return for several days. If I had been in town when the evacuation had been called, I might not have been able to get back to them even to top the water up. And of course the weather that week was hot, dry, and smoky.
The situation freaked me out enough, plus I had to cobble together everything I could find that held water, that I now actually have three small tanks for the sheep and three total of the 300 gallon tanks. Because we are on a well, we lose water when we lose power. At least we have a storage tank that can be siphoned (which is what we had to do with the fire coming) as well as a generator. But, you never know how much or how little time you’ll have, or if you’ll be in a position to actively prepare. So my advice is, have some sort of arrangement where the water will work without power and without humans for 3 days minimum.
On the plus side, this also is a huge help for me in normal times. I don’t have to fill the tanks every day. If I’m in a big hurry I may not need to do water every morning and every night, as long as I put my eyes on it.