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I wanted to throw this out to see what others thought.
I have had a severely over stocked pond for sometime. This year I added a UV to get rid of the algae problem. It worked unbelievably well. The new problem was ammonia, nitrate and nitrite swings...until string algae took over all the tops of my bio filters where my water Hyacinth used to be (another story). It is a thick soupy mess and I have tried to keep it clean to no avail. Now I leave it and scoop off some each day. My test readings have been great since. I estimate that I have a total of more than 6 gallons of string algae growing in the filters right now.
Do you think the algae is providing a significant impact on the nitrogen cycle? Should I let it be or try to replace with plants? Or any other thoughts
Thanks jpm

Interesting question. Since the nitrates are consumed by plants and algae as nutrients, then I would think the algae would contribute to the overall nitrogen cycle. How much its contributing, don't know since other factors need to be taken into account. The cycle can be affected by temperature, the level of oxygen saturation of the water and by the level of carbonates (kH) in the water. Have you measured the nitrate level in your pond and compared it to when you had the Water Hyacinth's? If it is the same then I would think the algae is doing its job, otherwise you would be doing larger water changes to reduce the level of nitrates. I don't remember all the filtration methods you are using on your pond, but if you have a TT then this could control the nitrate level thus giving you a false sense of how much the algae is contributing to the overall nitrogen cycle.

Though unsightly, string algae is a form of filamentous algae which is a beneficial type of algae that harbors good bacteria necessary for clearing the water.

An overabundance of algae in the pond can also be caused by excess nutrients such as organic debris, decaying flowers and leaves from pond plants, and/or too big a fish load. The one concern I may have is whether the string algae has an impact on your water flow.

I would probably feel safer to have plants in my filter system then relying on algae. Mainly because you never know when this stuff will all of a sudden decide to dye off. I guess your not using using Koi Clay?
Steve

Steve is correct, the string algae is using the nitrates to grow. Killing it off without adding more biofiltration will result in a spike in ammonia, and or nitrite and or nitrate.

This can be verified by running water tests, killing off the string algae with koi clay and then running tests again.

While many die hard koi lovers, those who compete in shows, will never have plants in their pond, they miss the important aspect of them. They are needed to keep nitrates low. In another thread the 2 of you were talking about TT (trickle towers) and many of the die hard koi folks use TT to keep the nitrates low.

While I do have many top quality show koi (ribbons and trophies to prove it), I much prefer to keep plants in my ponds and tanks to keep the nitrates low. Sure plants are a bit more work because of the maintenance of them and keeping up with decaying plant matter, I much prefer the look of a "planted pond" than the sterile look of a plant less pond.

Don't get me wrong, Rich and I have many friends who are into showing their koi and would never ever allow a plant near their pond, we have a mutual respect of each others beliefs.

Bonnie