It might be worth trying a pleco again. They tend to kick off if the water gets below the mid-50s I believe, so you may need to capture and overwinter him indoors (or take to a pet shop). That's hard to do with a brown fish...
One option to try (no guarantees, just might be interesting) would be a few kissing gouramis. By the time you'd want to net them out to save them from a cold winter, they'd be big enough to spot. I don't know how cold they can go, but they do eat algae and can cohabitate with goldfish. They're also quite pretty.
One option to try (no guarantees, just might be interesting) would be a few kissing gouramis. By the time you'd want to net them out to save them from a cold winter, they'd be big enough to spot. I don't know how cold they can go, but they do eat algae and can cohabitate with goldfish. They're also quite pretty.