Depending on what the problem may be there are different ways of preparing samples for diagnostic examination. Our ability to determine the cause of a problem is dependent upon the quality of sample received. In general we prefer samples be sent fresh, wrapped in plastic and put on ice, not frozen. The DNR has prepared this advice for avoiding or treating swimmer's itch. Duckweed can be removed by skimming or applying a DNR-approved herbicide.
Filamentous algae is composed of long, green threads often matted together, resembling green cotton.
Filamentous algae can be controlled with copper sulfate or other copper-based algicides. If it looks like green cornmeal, it is probably watermeal. If it cannot be swept aside with your hand and it is stringy, hairlike, or slimy or colors the water green or brown, it is likely algae. All rights reserved.