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60 • Nebraska Game and Parks Commission Muddiness due to Soil Type Water that stays muddy is likely due to the type of soil in the watershed. This is the most difficult problem to resolve. Clay particles in suspension actually repel each other, rather than clumping together and settling out. Surface application of certain chemicals or organic matter causes a chemical reaction that makes the clay particles clump together and settle out. These treatments typically only provide temporary relief. The pond will likely become turbid again when the next major storm runoff event occurs. The sources of sediment should be eliminated through proper land management practices. Ponds with chronic clay turbidity problems shouldn't be treated. Instead, they should just be stocked with channel catfish and minnows and provided with artificial feed, since turbid ponds produce limited natural food. See page 36 for further stocking and management information. Chemical Treatments: Alum (hydrated aluminum sulfate) Alum is the most effective treatment to remove colloidal clay. Alum causes the clay to flocculate and settle out. It also produces an acidic reaction. Alum should be dissolved in water and then applied on a calm day. Windy conditions cause mixing that prevents formation of floc and settling out. Alum should be sprayed over the pond surface from boat or shore. On large ponds, a dissolved solution can be sprayed or poured into the prop wash of an outboard motor. If the water doesn't clear within a day after an initial application of 25 pounds per acre-foot of water, a second 25-pound application should be made. If the pond is acidic (pH below 7.0) or has soft water, a similar application of hydrated lime (calcium hydroxide) should be applied first to protect fish from the alum's acidic reaction. Occasionally, the liming process alone causes the clay particles to settle out. Avoid inhalation or eye contact with both hydrated lime and alum, due to their caustic and acidic natures respectively. Pumps operate under high pressure during alum application, which can cause them to rupture. Agricultural Grade Gypsum (hydrated calcium sulfate) Gypsum is also used to remove colloidal clay and is available at many fertilizer dealers; however, it is less effective than alum or hydrated lime. It can be applied at rates of 100 to 525 pounds per acre-foot of water. It can be applied in 100-pound increments, waiting a few days between applications, until the desired visibility is achieved. Gypsum should be applied by the same techniques described for alum. It has a neutral reaction in water and doesn't require a lime treatment. It also doesn't affect the use of treated water for livestock or aquatic plant and animal life in the pond. Finely ground agricultural limestone can be used as a substitute for gypsum and applied at a rate up to 500 pounds per surface acre. It can be applied using similar techniques as gypsum and it has a similar reaction and low environmental risks. Scrap sheet rock containing gypsum can also be used. Organic Matter Treatments: Hay Bales Muddy water caused by suspended clay particles can sometimes be corrected by spreading broken bales of high-quality alfalfa, clover or prairie hay along the shallow, near- shore areas. About 100 pounds of hay (two small bales) should be applied per surface acre of water at 14 day intervals. As bacteria break down the hay, the resulting by-products form a weak acid, causing clay particles to clump together and settle out. Since decomposition uses up oxygen, this method shouldn't be used during the summer when water temperatures are high and dissolved oxygen levels are low or widely fluctuating, or late fall if hay will not be fully decomposed before winter. Dry hay bales should be used to facilitate a slower rate of decomposition. Monitor clarity changes. No more than 5 applications should be made