Pond Weeds – Pithophora & Rhizoclonium


Most filamentous algae control methods are similar, except for a few species. And these are one of them. This is a group of wide-spread algae that are difficult to control. Pithophora and Rhizoclonium are in the filamentous algae category. They resemble a mass of wet-green wool. Control with these types of algae is more complicated than other species.

If you ever see an algae that feels like wool when you pull it from the water, it one of these species. Pithophora may be more common. This is the first time I’ve seen Rhizoclonium. The only difference between the two is microscopic. In the water, we still need to pull samples to determine if it’s pithiphora or rhizoclonium.

Wool-like appearance

Wool-like appearance


Essentially, we can treat these “wool-like algae” the same. Use a tank mix of cutrine plus with diquat at ½ gallon each per surface cre. This pond is very, very small – probably 1/10 of an acre, if that. Weedtrine D is another choice for small ponds. It is a dilute formula of diquat that is about 1/10 the concentration of Reward or generic Diquat which are 2.0 pounds AI per gallon.

Could we use copper sulfate instead of Cutrine Plus?

Yes. This difference is that Copper sulfate is more toxic to fish in soft water. UGA Aquatic Scientist Dr. Gary Burtle says copper sulfate is okay as long as the crystals are dissolved. Add about an ounce of copper sulfate per gallon of water, and get most of it dissolved. We need to avoid using more than 4 ounces of copper sulfate per acre foot of water in a pond like this – which probably has hardness less than 10 parts per million.

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