Good old string algae. I snag some of it by hand or with a toilet brush AND I leave some of it for my goldfish to eat. In north Carolina it will freeze in a month or two and the algae may be their main food source. They seem to eat it now also, but perhaps they are just eating little snacks that get tangled up in it.

Should I remove them? Will they harm the other plants, or clog up the pump?

Chas,

I wondered why I had string algae (which I like a great deal) in the stream but not in the pond. Sometimes I would dislodge some string algae and see it flow into the pond but I never found any growing there.

Your post answers that ponder (no pun intended). The fish eat it when it flows from the stream into the pond.

Anne

newgen, I haven't found any problem in the pond from the string algae. Before my pond/stream was as balanced as it is now, I had other brownish algae that attached or tangled with my underwater plants and made them look dirty and dead. Now my string algae is mainly at or near the top and doesn't really tangle with them. Since your water appears clear, I would guess that you won't have a problem unless you find gobs of it around your pump housing.

Anne, I have a long stream and find the algae useful for traping crud. I remove a few gobs of algae with some crud and the part of the crud that escapes gets trapped by the rest of the algae and plant roots. I suspect that the combination of algae, roots and crud creates a soil base for the plants that helps anchor and sustain the plants.

In my original post I was cautious in indicating how much algae the fish would eat at this time of year. However, as I wrote it, I was running out of food and it has been several days before I could get to the pet store. In that period, the fish ate most of the obvious algae; so when there is a will there is a way.