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How to Clarify the Water in Your Pond with Recycled Gypsum

Does the water in your pond look cloudy, muddy or murky? While many ponds can appear murky or cloudy after recent rain or a sudden weather change, when the situation doesn’t clear up in a few days, there could be a bigger problem.

Cloudy, murky pond water isn’t just unattractive. It can also hide harmful debris from broken glass and trash, as well as dangerous wildlife. Muddy water also prevents sunlight penetration which is necessary to sustain food production for aquatic wildlife in and around the pond.

So what causes pond water to become cloudy or murky? The most common cause of cloudy, murky ponds is the suspension tiny dirt particles, mostly clay. The small size of these particles causes them to continually move around, rather than sink to the bottom. This results in water that is cloudy and muddy, with a stirred up appearance.

So How Do The Particles Get Stirred Up?

There are many factors that can contribute to sediment animation including:

Soil Erosion

Runoff from rainfall often dislodges clay particles, especially in areas with bare cropland, over-grazed pastures or exposed shorelines. Areas with compacted soils or soils on moderate to steep slopes are most prone to water erosion. Erosion introduces clay particles into the pond that cause a cloudy, murky appearance.

Animal Activity

Animals can also stir up clay particles, especially in shallow areas at the shoreline.


Whether on the shoreline or in shallow water, livestock can stir up large quantities of clay particles. They also contribute large amounts of manure to the water, creating further problems.

 Wild Animals

Feral hogs, deer, ducks and geese stir up bottom sediment along the shoreline or by entering shallow water.

Nuisance Fish

Bottom-feeding fish, such as bullheads, carp, or crayfish stir up bottom sediments when they dig, in search of food.

Weather Conditions

Rapid changes in air temperature, heavy precipitation, and high winds can create thermal currents that result in water movement that disrupts the sediment at the bottom of the pond. This is more likely in shallow areas, usually at the ends of the pond.

Any of these causes can contribute to cloudy or muddy water that persists for several days. However, if the muddy conditions continue for more than a week, it’s time to take some water samples and determine if water treatment could clarify the water.

Testing the Water

Fortunately, water testing is simple and inexpensive, using the Simple Bucket Test.

The Simple Bucket Test

  1. Fill two, 5-gallon buckets with water from your pond. Buckets should be placed indoors, away from direct sunlight. Add a penny-sized piece of drywall to one of the buckets. Leave the other bucket untouched.
  2. Check each bucket once every 24 hours to determine if the water has begun to clear.
  3. If the water clears in the water-only bucket, over a one week period, then your water clarity is likely being disrupted by something physical, such as animal activity or recent weather patterns.

If the water in the water-only bucket does not clear, then the cause of the problem is likely a chemical factor.

If the water in the drywall and water bucket clears, it is likely that an application of gypsum would clear the water and reverse the chemical factors affecting water clarity.

Treating Your Pond with Gypsum

Gypsum (CaSO4) is a water soluble mineral found in fertilizers, drywall, and plaster. Recycled gypsum is available in a variety of particle sizes for easy application. Since gypsum is pH neutral, it will not affect the water pH when added to your pond the way some aluminum sulfate treatments can.

Gypsum works by naturally attracting clay particles in the water to form clumps (floccules). As the clumps get larger and heavier they settle to the bottom of the water.

When you’ve completed the bucket test and determined that the addition of gypsum can help clarify the water in your pond, the next step is determining the proper amount to add. It is important to add only as much as you need to completely clarify the water, and no more.

Treatment Instructions:

  1. Obtain 6 identical, 1-gallon glass jars. Fill five of the jars with water from your pond. Set one jar aside to be used as a control for comparison. The remaining 4 jars will be treated with gypsum at different rates to determine the optimal rate for pond treatment.
  2. Fill the remaining empty jar with clear water to mix with the gypsum. Clear water can be obtained from collected rainwater or a nearby clear pond or stream.
  3. Using a standard measuring spoon, add two level teaspoons of gypsum into the gallon of clear water. Stir until the gypsum forms a slurry.
  4. Next, add different amounts of the gypsum slurry to each of your 4 test containers. Allow the jars to sit undisturbed for 12 hours. The minimum amount, which clears the water in the test containers, will be used as a basis to calculate the amount of gypsum you will need to clarify your pond.

Refer to the following chart from Texas A&M Agrilife Extension for guidelines:


While you won’t be able to account for every factor that could cause sediment stirring and cloudy, murky water, there are some steps you can take to provide the best conditions to maintain a clear pond.

Maintain the proper ratio between watershed and pond

It’s important to maintain a ratio of 10 to 15 acres of surrounding watershed per acre of your pond. However, the necessary watershed size can vary based on climate, soil type, and soil slope in the watershed area, as well as the depth of your pond. Maintaining adequate watershed will reduce the amount of sediment that enters your pond during significant rainfall.

Maintain vegetation in the watershed area

According to the Missouri Pond Handbook, “The vegetative cover in a pond’s drainage area greatly influences both the quality and quantity of water that run into the pond. Un-grazed timberland and stable grasslands provide the cleanest water source.”

In agricultural areas, establishing a vegetative buffer zone between your pond and crops or grazing areas is often the best choice. Vegetation buffers are able to trap sediment before it enters the water, contributing to greater water clarity.

If the only vegetation leading to the pond is cropped land, hay crops provide better erosion control than row crops do.

Avoid stocking your pond with nuisance fish

Carp, goldfish, bullheads and crayfish muddy the water by kicking up sediment at the bottom of the pond in order to find food. If nuisance fish are already present, it may be necessary to remove them in order to correct the water clarity issue. You can also stock your pond with largemouth bass or other predatory fish in order to control the population of nuisance fish.

Limit cattle access to your pond

Limiting cattle access will prevent bank erosion and the disturbance of sediment in shallow water. It will also prevent manure from contaminating the water.

Keep ducks and geese away from your pond

The webbed feet of both ducks and geese can continually stir up sediment, especially in shallow areas near the shoreline. The best approach is to discourage ducks and geese from foraging near or entering your pond. This can be done using air cannons or dogs to scare the birds away. Applying product to vegetation to make it unpalatable can further discourage ducks and geese. If you keep domestic ducks or geese, their access should be limited to one pair per surface acre of water.

Limit the introduction of organic matter or organic carbon to the water

While some farmers use hay or other organic matter to clear muddy waters, this practice often results in poor water quality and dead fish. The decomposition of hay and other organic materials, over time, leads to lower oxygen levels that can kill fish and other aquatic life. This is especially true during warmer months since warm water contains less oxygen than cold water.

Maintaining the clarity of your pond will likely be an ongoing effort, but with proper planning and the right tools, just about any pond can become a crystal, clear oasis for recreational fishing or just a quiet place to enjoy lunch on a sunny afternoon.

Looking for gypsum to treat your pond? Based in Lancaster County, PA, USA Gypsum provides high-quality, recycled gypsum, and ships nationwide, providing an all-natural solution to improve the water quality in your pond.

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