The most common lake weed problem is Filamentous Algae. Filamentous Algae, also called “lake moss” or “pond scum”, form dense mats of hair-like strands. Filamentous Algae is often a persistent problem because it reproduces rapidly by fragments, spores and cell division. Abundance is dependent on nutrient levels, particularly phosphorous, in the water. High levels of nutrients result in increased amounts of algae.
Its presence can degrade water quality and recreational enjoyment. Excessive algae can cause oxygen depletion when it decomposes, as a result of natural die-off or an algaecide application. This is often the cause of a fish kill, depending on how low oxygen levels get. A healthy pond can be achieved with early and regular control measures.
Pond algae removal can be accomplished by physically lifting large floating clumps with a rake. Mechanical removal is an ongoing activity during the growing season due to the algae’s persistent fast growth. Pond algae removal will result in large piles that can be reused for composting or garden mulch.
One method of biological control is to fertilize your pond to encourage the development of planktonic algae that will reduce water clarity. Reduced clarity means less sunlight reaching the pond bottom, which in turn reduces growth of filamentous algae. This requires intense management.
Another method of biological control is to reduce watershed or outside sources of nutrients. Algae get their nutrients from the water, so minimizing nutrient levels is a worthwhile management activity. Common sources of unwanted nutrients are Canadian geese, lawn fertilizer, domesticated animals, agricultural fertilizer, and even septic systems if located too close to a pond. Pond muck removal can be accomplished with a natural bacteria applied weekly until desired water quality is achieved.
Selecting a chemical to control Filamentous Algae is situation-specific and the pond owner needs to consider several factors. The most important factors are the water uses provided by the pond and any use restrictions associated with the products. For a list of optional control methods call Aquacide Company 800-328-9350.
Applying the correct amount of chemical is crucial to successfully controlling algae. All product labels provide dosage or application rates, often as pounds or gallons per acre-foot of water. For more information on calculating acre-feet consult your county extension service or call us directly.
Timing of chemical applications is another important consideration. Some algae species can reach nuisance levels in cold water just after ice-out. However, many algaecides work best in water warmer than 60 degrees F, and use in colder water will yield less than desired results.
Algae reproduces rapidly, and it is common not to get season-long control with algaecides. Nearly all products provide 3-4 weeks of improvement. Retreatments are often necessary. It is better to do numerous small scale retreatment’s rather than allowing the algae to cover large areas. This reduces the risk of a fish kill as well as being cost-effective.
Inert dyes can be used to control Filamentous Algae. The color they turn the water, usually blue, reduces sunlight penetration, which in turn reduces growth of algae. These dyes are not effective in water less than 2 feet deep. Application is very easy and should occur early in the growing season, preferably in March. Inert dyes are not recommended for use in ponds with considerable water exchange during a rain. Most inert dyes are labeled for all water uses except domestic drinking water supplies.
For complete article see: "Controlling Filamentous Algae in Ponds," William E Lynch Jr. Ohio State University
Filamentous Algae, Wikipedia – free encyclopedia