Filamentous Algae


Description:  Blue-green, black, brown, and dark green; filaments are similar in size to coarse hair and mats are a tangle of filaments, slimy or coarse; toxin and taste/odor producer; smells dirty/fishy. Forms benthic and surface mats.

Similar Mat Forming Blue-green Algae: Phormidium, Scytonema, Leptolyngbya (finer mats, tan color)

Control Method Needed: Captain



Description:  Blue-green, brown green, lime, orange; can have an earthy musty smell; unbranched, filaments that typically form mats; can form sheets/films on surfaces of many types of materials (sediment, rocks); some species are planktonic; toxin and taste/odor producer.

Control Method Needed: PAK 27, Captain


Pithophora (horsehair/cotton algae)

Description:  Course, tough mats; filaments branched; dark akinete cells; feels similar to a bundle of cotton. Forms dense, dark green mats along the bottom and surface.

Similar Mat Forming Green Algae: Rhizoclonium (rarely branched), Cladophora (Blanket weed)

Control Method Needed: Captain, SeClear


Spirogyra (silk algae)

Description:  Slick and rigid filaments, size of coarse hair; bright/deep green; benthic and floating mats/tufts.

Similar Algae: Mougeotia, Oedogonium, Zygnema

Control Method Needed: SeClear, SeClear G