How to Get Rid of Moss or Seaweed in a Man-Made Lake

Remove the seaweed manually. Wear a pair of waders and carefully step in the lake. Grab the seaweed and pull it vigorously out of the lake. Do not toss the seaweed into the lake. Instead, place it on the bank and either compost it or place inside a garbage and dispose.

Skim the surface of the lake with a rake. The teeth of the rake will grab the seaweed so you can pull it back toward you.

Add grass carp to the lake. Grass carp consume algae and aquatic plants including seaweed and will remove the seaweed without chemicals. Certain areas require a permit for grass carp. Contact the local Department of Natural Resources (DNR) for information on owning grass carp.

Use a pond aerator to keep the water in your lake moving. Moving water reduces the chance of seaweed growth. Pond aerators come in a variety of sizes and brands and are available for purchase at home and garden centers.

Apply black or blue pond dye to your lake. Pond dye suppresses weed growth by darkening the color of the water, which reduces the amount of sunlight. Without proper sunlight, seaweed cannot grow. The pond dye will not harm plants, fish or other aquatic life.

Use an herbicide, such as copper sulfate, specifically designed to eliminate seaweed. Read and follow all directions and warnings printed on the herbicide bottle. You can purchase herbicides at home and garden centers.