|
 Most pond owners would probably agree that having clear water adds to the aesthetics of their pond. The clarity of pond water is primarily influenced by the abundance of microscopic plants (phytoplankton), animals (zooplankton), and suspended soil particles. Phytoplankton and zooplankton abundance will influence the water clarity to varying degrees depending primarily upon the time of year, time of day, and fertility of the pond. Generally, these tiny plants and animals do not influence water clarity as significantly as suspended soil particles. “Muddy” water is the result of tiny soil or clay particles suspended in the water.
Muddy water can have negative effects other than detracting from the aesthetics of the pond. Muddy water can hinder the feeding ability of largemouth bass, bluegills, and redear sunfish and even reduce their growth. Additionally, phytoplankton growth and abundance is reduced in muddy water. This may compound the problem of poor fish growth in muddy ponds by reducing the amount of food available through the entire food chain.
The first step in correcting a persistent problem with muddy water is to determine the cause. To do this, collect a jar full of pond water, cover it with a lid and allow it to sit undisturbed for one week. If the water appears clear after one week and sediment is noticed at the bottom of the jar, chances are that something in the pond is stirring up the sediments. However, if the water is still cloudy, then there is a good chance that
suspended particles of clay soil are the cause of the muddy water. The problem may also be a combination of disturbed sediments and the presence of clay soils in the watershed.
If disturbed sediments are determined to be the problem, one or more of the following suggestions may help remedy the situation: 1) Remove undesirable rough fish from your pond. Bullheads and common carp have a habit of “rooting around” in pond sediment while feeding. Channel catfish may also cause the same problem. 2) Fence livestock away from the pond and avoid pasturing them on the pond’s watershed. Livestock trample and compact pond banks causing them to erode. 3) Establish moderate vegetative growth of rushes, sedges, and cattails to protect pond banks and shoreline areas from wave erosion. 4) Keep domestic ducks and geese away from the pond. Their feeding activity may destroy shoreline vegetation and resuspend soil particles from the pond bottom. 5) Maintain good vegetative cover throughout the watershed. If you do not have ownership of the entire watershed, then establish buffer strips of vegetation around the pond. 6) Plant windbreaks to prevent wind from causing excessive wave action and disturbing sediment in shallow water. These suggestions offer the best long-term protection against muddy pond water. It is much easier and cost effective to prevent soil particles from eroding into a pond than it is to remove them once they become a problem.
If the previous methods prove unsuccessful, it is likely that the muddy water problems are caused by colloidal clay particles that stay in suspension for a long time. Since colloidal clay particles do not settle out easily, other techniques are necessary to improve water clarity. Several techniques are effective at removing colloidal clays from pond water. Each technique requires the addition of various materials to the pond that cause clay particles to settle out. These additives include organic matter (hay), aluminum sulfate (alum), calcium sulfate (agricultural gypsum), and hydrated lime. Each of them work through a chemical reaction that causes suspended clay particles to “clump together.” These “ clumps” of particles are heavier than individual particles and therefore sink rather than stay suspended. Most of these additives can be purchased from local agricultural supply stores.
Hay Bales. Application rates of dry hay are recommended at 540 pounds per acre-foot of water (see Chapter 4 to calculate acre-foot volume of a pond), which is roughly equivalent to 7 to 10 dry bales depending upon weight of each bale. Hay bales should be broken up and scattered evenly along the shallow nearshore areas of the pond. Applications should not be made for the entire volume of water at one time. Instead, apply treatments equivalent to one acre-foot of pond water at a time and monitor clearing. Each treatment should be separated by a two-week period. This method should not be used during July and August when water temperatures are high and dissolved oxygen levels in the pond can fluctuate widely from day to day. The best time for treatments is in the spring or early summer when oxygen levels are consistently higher. This method is not recommended for ponds that have a history of fish kills.
Aluminum Sulfate (Alum). Alum is the most effective treatment for clearing muddy water caused by colloidal clays. Application rates for alum are recommended at 25 to 50 pounds per acre-foot of water depending upon the concentration of suspended clay particles. The first treatment should be made at the rate of 25 pounds per acre-foot. Clay particles should settle and the water should clear within a few hours after mixing the alum. If there is little noticeable change after one day, then a second application should be made at 25 pounds per acre-foot. Alum should be applied during calm weather to avoid wind mixing that prevents clay from settling out. It is most effective when dissolved in clear water and sprayed over the surface from shore or a boat. In large ponds, a dissolved solution of alum can be poured into the outboard motor wash of a small boat.
Alum can reduce the pH and alkalinity of pond water due to a strongly acidic reaction in water. For this reason, pH and alkalinity need to be tested before treatment with alum to prevent harmful effects to fish. Alkalinity should not be below 75 mg/l and pH should not be below 7.0. If readings are found to be below these levels, then hydrated lime should be added in the same manner as alum at the rate of 50 pounds per surface acre. This will help buffer the acidic effects of alum treatment and protect fish. Alum is only toxic to fish under these conditions or when used at very high concentrations for a long period of time. Hydrated lime will also help remove suspended clay particles.
Agricultural Gypsum. Agricultural gypsum (CaSO4 2H20) can also be effective at removing colloidal clay suspensions from ponds. Application rates range from 100 to 522 pounds per acrefoot of water depending upon the amount of suspended clay. It is best to first apply gypsum at the most conservative rate of 100 lbs/acre-foot, and allow a few days to pass while monitoring water clarity. If the pond has not cleared, apply additional gypsum until transparency reaches 18 inches or meets owner satisfaction. Gypsum should be applied by the same methods described for alum, although it has a neutral reaction in water and does not require simultaneous lime treatment. Another advantage of gypsum is that it does not affect the use of water for livestock and will not affect plant and animal life. However, gypsum is less effective at removing suspended clay particles than alum or hydrated lime.
Hydrated Lime (Calcium Hydroxide). Hydrated, or slake lime, can also be used to reduce muddy water. Application rates are suggested from 35 to 50 pounds per acre-foot with application methods similar to alum and gypsum.
|