Filamentous algae are single algae cells that form long visible chains, threads, or filaments. These filaments intertwine forming a mat that resembles wet wool. Filamentous algae starts growing along the bottom in shallow water or attached to structures in the water (like rocks or other aquatic plants). Often filamentous algae floats to the surface forming large mats, which are commonly referred to as “Pond scums.” There are many species of filamentous algae and often more than one species will be present at the same time in the pond. Pithophoria is commonly called the cotton ball algae. It can be obsereved floating on the surface looking like a very coarse green cottonball. It is one of the more difficult filimentous algaes to control.
Submerged portions of all aquatic plants provide habitats for many micro and macro invertebrates (i.e. bugs, worms, etc.). These invertebrates in turn are used as food by fish and other wildlife species (e.g. amphibians, reptiles, ducks, etc.). After aquatic plants die, their decomposition by bacteria and fungi provides food (called "detritus") for many aquatic invertebrates. Filamentous algae has no known direct food value to wildlife.
Herbicide Management Options:
Chelated Copper Algacides: Cutrine Plus, K-Tea, Captain, and Clearigate are all chelated or compound copper herbicides that are effective on filamentous algae. Other chelated or compound copper formulations are available but are not linked to this web site.
All copper compounds can be toxic to fish if used above labeled rates and can be toxic in soft or acidic waters even at label rates.
Fertilization to produce a phytoplankton or algal “bloom” can prevent the establishment of filamentous algae if started early enough in the spring. Fertilization also produces a strong food chain to the pond fish. You should never add fertilizer to a pond with auqtic weed issues, doing so will only make the problem worse!
Non-toxic Pond Dyes or colorants prevent or reduce aquatic plant growth by limiting sunlight penetration, similar to Fertilization. Cygnet Select, Aquashade, and Crystal Blue are examples of non-toxic dye and other products are available.
Biological Management Options:
Tilapia: Will consume Duck Weed but are a warm water species that cannot survive in temperatures below 52 F. Therefore, Blue Tilapia usually cannot be stocked before mid-April and normally die in November or December. There are numerous reports of Blue Tilapia overwintering in mild South Carolina winters. Recommended stocking rates are 100 - 200 tilapia fingerlings per surface acre of plant biomass of mixed sex adult Blue Tilapia. Blue Tilapia is often not effective for vegetation control if the pond has a robust bass population due to intense predation. In South Carolina, stocking of Tilapia requires a permit from the South Carolina Department of Natural Resources. AMS is licensed to provide these permits for you.