My experience here in Oregon is that algae doesn't grow much at all when the water gets cold. All of the biological activity in a pond slows down when the water gets cold, so I don't think leaving some live algae in the water would be a problem, especially since your pond doesn't ice over. Your reference to "algae masses" does make me wonder how much algae you are talking about though. If there is too much algae, it might be smart to get most of it out.

In general I don't think a little algae hurts a thing in ponds, although some kinds of algae might be worse than others. Mostly, I look at algae as an indicator that points to other pond health issues. If you look at algae as an indicator and concentrate on the other issues, the algae will usually take care of itself.

I guess I could have called them algae "clouds" instead. They look like green cotton candy growing off the bottom shelf on one side - a sunny side away from the direct stream of the waterfall. When I use the rake to scoop them out, there is very little actual fibrous algae - it kinda melts down to a thin film on the ground, and feels/looks exactly like the regular string algae near the waterfall. The fish easily swim in and out of it, and I can see the fish inside it. I've heard string algae is a sign of healthy pond water. ??? There is not too much - just some stretching out from the waterfall and this long cloud on the side that gets direct sun, has no plants, and less water movement. Definitely not as bad as in the Spring when I'm scooping once a week from all sides. I thought it might help hide the fish since the plants have died back, but there are plenty of caves and castles for them to retreat to, so I'm fine with scooping out the cloud - it won't all come off - it's sticky little tendrils are attached to the rocks. I had considered leaving it since the smaller (gold)fish seem to be hanging around underneath it instead of in the castles and hide-aways.