If you water needs to be treated before use...as most does...then you use a storage container of some type to store it, treat it and heat it to desired temperatures before use...but that takes up a lot of space. My house has a basement under one half, and just a crawlspace under the other half. I have 55-gallon barrels and a big water storage tank in the crawlspace and keep them filled; they take a day or so to reach ambient basement temperature, which is also what my tanks are kept at, and then the water can be drained into whatever tank needs it. The catch is that once I use it all, I need to wait for the next batch to warm up before I can do more water changing, and I don't have enough storage capacity to be able to do a water change on all tanks at once.
I recently installed an on-demand tankless water heater in my home, and took the opportunity to install hot-and-cold taps in the basement, and another set outside. This way I can get water mixed to whatever temperature I want, in essentially unlimited quantities. Total game changer; I love being able to do fin-level water changes in all tanks at the same time. The outside taps make filling tubs, ponds and other containers easy, and is handy for bathing the dog, rinsing filter foam and many other jobs that are unpleasant with just cold water. On-demand heaters are great for this; if you have a traditional tank-style water heater, you are still limited in the amount of heated water you can get at any given time; if your pond/tanks are big enough, and/or your water tank too small, you still might not be able to get as much water as you would like at one time.
My single indoor "pond"...a round stock tank 72 inches across...is only used in the winter for outdoor fish that must overwinter indoors. I filter it with a single homemade giant Poret sponge filter, 6 x 6 x 19 inches, powered by air. Works like a charm, easy to remove and rinse out...especially now, with warm water!

...and inexpensive compared to any type of power filter.