Filamentous Algae aka Blanketweed aka String Algae

We get questions:


Hi, It's me again.

I worked furiously in March to clean out my pond, and you all were a great help. However my enthusiasm, and your great help did not prevent the weather in PA from going cold for the month of April. So I let my pond sit, with the waterfall going 8 hours a day from mid March to now.

I have been calling nurseries around here waiting to get some new plants in there, and then once the plants came in I would put in the fish (I found a guy for that too) however, looking at my pond 2 months after the clean out i see what looked like a green haze, or some fine green cotton candy, I pulled some out and see that it is more like seaweed.

Is this good (that I have food for my future fish), or is this bad (that all the stuff I tried to remove in March is coming back), or something in between?

FYI the nurseries around here are claiming that the water plants should not go in until memorial day.

Thanks in advance



ANSWER

That is filamentous algae. Which species it is is difficult to determine without a microscope. Note that it is most abundant just below the waterfall, where there is a strong current. It likes moving water. Your pond area looks susceptible to influx of nutrient from rain runoff. Nutrient runoff into the pond, especially phosphorus, is the likely source of your algae growth. With your small pond, the best treatment is to first stop the runoff into the pond and then manually remove the algae. I suggest the use of a toilet brush.

Here is a good article on filamentous algae in ponds:

Filamentous algae


More discussion:

After you remove as much of the string algae as you can, you can use Microbe-Lift PL to keep it gone.  H202 works too. Also I have poured a can of beer in a week and that works. Cheap beer.

But the fish do love to eat it.  It's we humans who think it's awful.

Put plants in your pond after the last danger of frost has passed.

You can read more about blanketweed, aka filamentous algae, aka string algae in my new book, A Practical Guide to Building and Maintaining a Pond" Download it here


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