I tried bringing my patio pond inside the first year in an attempt to overwinter my plants - it was largely unsuccessful and a big pain. My plants survived, but they did not thrive. They were actually pretty good up until the last few weeks when they started to fail fast. Like you, I don't have a spot with a lot of sunshine, but they were in a southern exposure window. By the time I could finally get them outside again, they were really, really sad looking and it took most of the early summer for them to recuperate. They didn't really look really good again until the season was almost over. Plus the spitter was too splashy (I had a couple of goldfish in mine, too) the aerator was too noisy and in general it just didn't belong inside.
So there's my review on that experience! I decided the few dollars I spent on new plants every year was well worth it. And the last few years I've actually just moved a few things from the big pond once the plants get started, so I only need to buy one or two things to add. I overwinter the lily in the big pond, which is simple, pull some of the parrot's feather, dig up some of the dwarf cattails and obedient plant, buy one big plant and it's a tiny pond!
