Using aquatic dyes in ponds

Pond dyes can be used year-round. Blue dye in ponds is shown to not harm animals or floating and emergent plants in ponds.

November 8, 2016 - Author: ,

Goldfish pond with blue aquatic dye. | Photo by Beth Clawson
Goldfish pond with blue aquatic dye. | Photo by Beth Clawson

Many open bodies of water experience algal blooms during the spring and fall seasons when the weather changes. This flush of algal growth occurs when the seasonal winds and temperature changes stir the water, bringing up sediments from the bottom and creating an addition of fresh nutrients to the water. This turnover process is normal but can cause your lake or pond to turn green or brownish green during these times.

This event is typically short-lived, and the water clears up again in a few weeks if additional nutrients from outside the lake are minimal. However, if nutrients are entering the lake, the blooms may persist. If you live along the pond or lake shore, you can help control nutrient input by adding buffer zones around your pond to reduce nutrient runoff. This type of activity is considered long-term, since you are addressing the problem. For near immediate relief, you might consider some short-term methods for decreasing the algae and managing your natural pond, such as adding a dye to the water.

Small pond owners can add a non-toxic dye to the water to help control the excess algae growth. It is common to see dyed water in public and recreational establishments, such as golf courses, recreation parks, ornamental ponds and decorative fountains. Aquatic dyes add blue or blue-green color to the water to reduce sunlight penetration. When used as a shade, dyes help to reduce growth by blocking photosynthesis.

There are several products on the market for this purpose. Dyes are found to be most effective in controlling filamentous and blue-green algae. Pond dyes contain colorants that are similar to food dyes and are not considered harmful to wildlife. It is important to note that there are some things an aquatic dye won’t do. Aquatic dyes are not herbicides, and it is unreasonable to expect these dyes to kill the plants in your pond. While dyes don’t hurt fish or other aquatic animals, they can affect desirable submergent plants that fish and other aquatic life may use for food and habitat. 

There are three common dye colors available for use: blue, black and a mix of the two imparting a deeper color to the water. The black dye is often used in the winter to give the pond or water feature a more reflective property. The blue/black mix is recommended for a more natural look, adding depth. Dyes can be used year-round and, if used, should be part of an overall pond management tool. If the pond has invasive species present, excessive weed growth or excessive nutrient loading, these problems need to be addressed for optimum control. It should be remembered that a pond should have a balance of plants, algae and other organisms present. These are key ingredients for a healthy aquatic ecosystem.

For more information about aquatic invasive species, lakes and ponds, contact Beth Clawson, MSU Extension educator. To learn more about invasive organisms and invasive aquatic plants, contact Michigan State University Extension Natural Resources educators who are working across Michigan to provide aquatic invasive species educational programming and assistance. You can contact an educator through MSU Extension’s “Find an Expert” search tool using the keywords “Natural Resources Water Quality”.

Tags: conservation stewards program, msu extension, natural resources, water quality


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