I will be treating for chara this spring and I'm using the Cutrine granules. I'm going to apply it when the water temperature warms to at least 60 degrees, from what I've read this is when chara starts to grow. Some info on algae below.

Quote:
Use CUTRINE PLUS Granular to easily control bottom algae or algae growing within 3 feet of the bottom. Cat litter size granules settle on algae and immediately begin attacking growth. Ideal for use on Chara. Makes early season spot treatment of Filamentous Algae a snap! Early treament will help prevent the formation of heavy surface mats.

For best results, use under conditions of minimum water flow. Apply early on the morning of a calm, sunny day. Contact time should be at least 3 hours.

To apply simply broadcast granules uniformly over the water surface. Use 30 lbs. of CUTRINE Granular per 0.50 acre. Broadcast by hand or by using a mechanical spreader.

Treat heavy infestations in sections to avoid oxygen depletion. CUTRINE PLUS granular is very effective on bottom growing algae. For Chara algae control this is our number #1 recommendation. Chara should be treated in spring and summer or when weed is soft and supple. Mature, established Chara may become calcified in hard water and very difficult to control.

A single early application will usually control Chara for an entire season. Bottom growing Filamentous Algae may require re-treatment for season long control. There is no minimum water temperature recommended for use.

From here: http://www.aquaticbiologists.com/cutrine%20plus%20granular.shtml

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