Clearing Muddy Ponds with Gypsum

If you have followed the watershed and pond management procedures outlined in the Pond Handbook, and have failed to get a clear pond, try agricultutal gypsum. Gypsum clears muddy water by causing the tiny soil particles to clump together and settle out. Once clear, a pond will stay clear until more mud is washed in or stirred up. Remember, there is no point in applying gypsum to a pond unless livestock are kept out or unless bullheads and in the watershed must be controlled.

Materials and Equipment

Agricultural gypsum (enough to apply 12 pounds per 1,000 cubic feet of water), a small shovel and a boat (on all but the smallest ponds) are needed.

Procedure

Calculate carefully the amount of gypsum you nesd. The surface area of a pond in square feet equals the average width multiplied by the length in feet (obtain Missouri Department Conservation pond area calculator). Convert this to acres, or fraction of an acre - 1 acre equals 43,560 sq. feet. Consider the average depth equal to 1/3 the greatest measured depth. Then refer to the dosage chart. Example: for a 1/2-acre pond with an average depth of 4 feet, you would need 1,050 pounds of gypsum.

Use a small shovel to spread the gypsum. Spread it over all the pond as evenly as you can: good results depend upon even distribution.

Very muddy water often clears up in less than a week. If the pond is just moderately muddy, it may take two to four weeks before you can sse results. If the water does not clear up within six weeks, and if there is no wave action, erosion or other source of muddiness, give it another application - this time about 1/4 the original dose. Again, be sure you have stopped all sources of erosion.

Precautions

Do not add more gypsum if the water is clear. It may be necessary to add one or two bags each year if the water appears dingy. Do NOT use alum, cement or wall plaster to clear ponds; they are too likely to kill fish.

Number of lbs. of gypsum to use to clear ponds at the rate of 12 lbs./1000 cu. ft. (Figures rounded off to the nearest 50 pounds)
Average Depth of Pond in Feet 1/4 1/3 1/2 2/3 3/4 1 1-1/4 1-1/3 1-1/2 2
2.0 250 350 500 700 800 1050 1300 1400 1550 2100
2.5 300 400 650 900 1000 1300 1650 1750 1950 2600
3.0 400 500 800 1050 1200 1550 1950 2100 2350 3150
3.5 450 600 900 1200 1350 1850 2300 2450 2750 3650
4.0 500 700 1050 1400 1550 2100 2600 2800 3150 4200
4.5 600 800 1200 1550 1750 2350 2950 3150 3550 4700
5.0 650 900 1300 1750 2000 2600 3250 3500 3900 5250