What is the source of cloudy water?
Cloudy water, also referred to as “turbid” water, can develop for multiple reasons such as excess algae or sediment. Planktonic algae, a microscopic, free-floating algae that exist in the top few feet of a pond can sometimes give the pond a green or brown coloration and tends to have rapid growth (or blooms) in the warmer months. Planktonic algae are an essential part of the food chain for fish and other aquatic creatures. To determine if the source of your pond’s cloudiness is algae or sediment take a sample of the water in a clear glass and hold it up to a bright light. If you see a lot of organisms moving erratically, you likely have a planktonic algae bloom and the organisms are zooplankton that feed on the algae. Unless you notice an increase in fish kills, a strong odor or unsightly surface scums, no management is needed.
Cloudy water may also develop from sediment and can be common after pond construction, a rainstorm or high winds. Some feeding activity of fish such as Common carp (not triploid grass carp) can cause cloudy water, as well as waterfowl or livestock access to the pond. Cloudy water can also result from the suspension of the smallest soil particle, clay. Suspension means that the clay particle will not settle and can give the water a muddy appearance. Cloudy water from wind, rain or animal activity should clear within a few days, however if the source is suspended clays may not. Cloudy water from sediment can be detrimental to fish populations by decreasing oxygen in the water; cloudy water can limit the sunlight reaching submerged aquatic plants, and thus, their ability to photosynthesize and produce oxygen.
To determine if the source of your cloudy water is suspended clay particles first take a water sample and let it sit undisturbed for 24 hours. If the sediment settles and clears, the problem is likely re-suspension from some type of activity (like fish or livestock). If the sediment remains suspended the problem may be due to the chemistry of the water and chemical treatment of the water may be necessary.
Prevention: The Best Pond Management
Your pond is part of a watershed. That means that water (with sediment, nutrient, pollutants) from the surrounding area moves through groundwater and surface water into your pond, and downstream to other waterbodies.
The best way to manage sediment is to limit erosion by planting a buffer area directly around the pond. Native perennials with deep root systems that do not lay down during big rainstorms are best. You can directly transplant native plants, or you can encourage native plant growth with reduced mowing. Limit mowing around the pond to every other year, and alternate mowing between spring and fall, to discourage unwanted annuals. The buffer should be a minimum of 15 feet wide, and up to 100 feet wide for steeper slopes.
Unless the source of the nutrients entering your pond is dealt with, you will likely have annual problems with excessive sediment and/or aquatic vegetation. Other preventive recommendations include:
- Fence off the pond from livestock
- Discourage geese around the pond
- Lining shorelines with rocks (often called “riprap”) to prevent both erosion
- Build a small settling basin upstream to intercept soil particles
- Plant a windbreak with trees and/or shrubs up wind of the pond
Management for suspended clay particles
First, make sure that the source of the cloudiness is suspended clays by taking a water sample. If sediment does not settle to the bottom after 24 hours, it is likely a chemical imbalance that is contributing to the suspended clays. Gypsum (calcium sulfate), epson salts (magnesium sulfate), aluminum sulfate (alum), or limestone (calcium carbonate) are all options for treatment.
A water test of the pond pH is first recommended for choosing a product to apply, as aluminum sulfate particularly can decrease the pH and damage fish populations. Gypsum is a neutral salt and will not affect the pH of the pond.
The following publication from Texas A&M University takes you through determining the amount of gypsum to apply: http://publications.tamu.edu/WATER/SCS-2013-02.pdf. You'll need to do a little experiment with a few jars of the pond water, applying a range of gypsum amounts, to determine the correct amount. You'll also need to do some calculations (given the size, depth and shape of the pond) to determine how much pounds per acre foot of product to apply. After application the pond should clear within 24 hours.
- Summary of water quality concerns for ponds: https://extension.psu.edu/water-quality-concerns-for-ponds (Penn State Extension)
- Control of clay turbidity in ponds: https://wkrec.ca.uky.edu/files/muddyponds.pdf (Southern Regional Aquaculture Center)
- Common pond problems: https://extension.okstate.edu/fact-sheets/common-pond-problems.html (Oklahoma State Extension)