Does Salt Kill Algae?

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Control string algae in ponds with salt.

When you create a water feature in your garden such as a pond or have an aquarium in your home, you will most certainly have to deal with algae. This material, a member of the plant family, is common in ponds and fish tanks due to just the right conditions for it to grow. One way to get rid of algae is though chemical treatments. Conversely, if you want to get rid of algae naturally, you can use rock salt to kill some algae.


Algae grow in ponds or aquariums where water is stagnant, where it reaches ample sunlight and receives the nutrients it needs to thrive. Some nutrients that feed the algae include fish food, fish waste, debris and decaying matter like dead fish and leaves. Algae can cloud the water and/or it can develop into string-like algae. You can get rid of these stringy algae naturally by adding rock salt to the pond.

Water Circulation

Water circulation decreases algae growth. When water circulates in a pond, the large debris that gathers there and contributes to algae growth gathers at the filters. Once there, you need to remove it with a net or by hand if you can reach it; otherwise additional algae will grow.

Balance in the Water

A balance of bacterial growth in the water is necessary for a healthy environment for water plants and animals. A smooth growth of algae will develop and coat the sides of the pond or tank. As strange as this sounds, this is actually what you want as it helps maintain the balance in the water where this good bacteria on the walls works to clear the pond of the debris that can cause a lot of algae to cloud the water. As the wall algae works away at the nutrients, the plankton or cloudy water that algae are fond of, you may find stringy algae floating in the water.

Using Rock Salt

Other than placing your pond in a shady area where it does not receive ample sunlight, you can use rock salt to kill algae. Laguna Koi Ponds recommends 1 lb. of rock per 1,000 gallons of water to kill the string-like algae. Use caution when using salt as it can kill plants and fish in the pond. Remove the plants from the pond before adding the salt. Plants exposed to the salt will decay and can contribute to the debris that algae love so much.


Stephanie Rempe

After attending the University of Missouri St. Louis, Stephanie Rempe worked as a documentation manager in the finance industry 10 years before turning to her first love, writing, which she's been doing professionally since 2008. She currently divides her time between Missouri and her fiance's hometown in Oregon. In addition to her freelance writing, Rempe is working on a romance novel and short stories.