Introduction
There are a number of causes for murky, fouled water in ponds. The most common are algae and suspended particulates, both organic and inorganic. The worst of these in terms of fouling the waters, by far, is algae.

Algae are almost ubiquitous in the biosphere and makes up a large portion of the total biomass on earth. They are a vital component of the biogeochemical cycles and provide a food source for many forms of aquatic life. They are extremely adaptable, living at the polar ice caps at sub-zero temperatures as well as in hot sulfur springs at temperatures exceeding 400 degrees F. Algae can be observed as single cells, e.g. cyanobacteria, which make water appear green and turbid; as filaments that looks like strands of hair; or massive clumps of seaweed. They can flourish in freshwater as well as brackish water. And some people wonder why it is difficult to control.

Particulates can come from two sources. Inorganic particulates can enter a pond or lake through runoff, be deposited by wind or streams that may empty into a pond or lake. Organic particulates can be formed as certain flora and fauna, for example algae, die off or as bacteria grow on this or other decomposing organic matter.

Characteristics of Algae
There are thousands of different types of algae, but all have certain things in common. First, they are photosynthetic, which means they are capable of using carbon dioxide as their primary source of energy and carbon. Some algae can also fix nitrogen, the macronutrient required in the greatest concentration. Being able to fix carbon and nitrogen makes algae very adept at surviving without a lot of outside help.

Like most photosynthetic plants, algae give off oxygen that can be beneficial to the overall ecology of the pond. However, when algae blooms are heavy they can degrade not only the aesthetics of the pond, but interfere with the ecology and functionality of the pond as well.

The most common forms of algae in pond are filamentous algae and planktonic algae. The filamentous algae, also referred to as hair or string, are usually the most problematic since they cause the mats and clumps that are not only unsightly and foul smelling, but can also clog pumps and filters. The planktonic, or free swimming algae, are usually associated with "green" water and are mostly cyanobacteria.

Some of the most commonly found nuisance algae in ponds include the filamentous algae Spirogyra, Pithophora, Chara, Nitella and Hydrodictyon (also known as water-net”). The common cyanobacteria include Oscillatoria, Anabena, Microcystis, Anacystis, and Lyngbya.

Conditions That Promote the Growth of Algae
Like most photosynthetic plants, algae fixes inorganic carbon and converts it to sugars that can be used as a source of energy and organic matter. If sunlight, nitrogen and phosphorous are abundant, along with some trace minerals and metals, e.g. iron, algae will usually flourish. Temperature is also a factor, as most common pond algae tend to thrive in warmer weather.

Minimizing Proliferation of Algae

Control Buildup of Nutrients Where Possible

Since turf (grass) comprises photosynthetic plants, it requires many of the same conditions and macronutrients as algae, often more since turf usually can’t fix nitrogen. Frequently, ponds are located on low-lying areas of the farmland and golf course, which means that the runoff often contains nitrogen and phosphorous in the form of fertilizer makes its way into the pond.

Ways to minimize the amounts of nutrient runoff into ponds include using an organic fertilizer that is not as water-soluble and which will, therefore, release nitrogen and phosphorous more slowly. Recent studies with humates have also shown that these compounds can sequester many of the nutrients in fertilizers and release them as the turf requires them, cutting down on fertilizer use and runoff pollution.

It also helps to physically clean out the dead or decaying vegetation in ponds or lakes where there is extensive vegetation or algae blooms, as this composting process will release nitrogen, phosphorous and other nutrients back into the water feeding another cycle of algae blooms.

Chemical Algaecides

There are a number of chemical agents for controlling algae. Among the most common is copper sulfate. Copper sulfate dissociates to the copper cation and sulfate anion in water. The copper, being a heavy metal is toxic to most living things. Like most chemical algaecides the result is often observed quickly at relatively low concentrations of copper.

When taken up by the algae the copper interferes with the metabolism at a cellular level resulting in the destruction of the algae. Once the algae dies off and decomposes the copper, like most heavy metals, persists in the environment. Over time this copper can build up in lake sediments and become toxic to aquatic life and render dredge spoils a toxic material if the levels of copper get high enough. Most states have outlawed the use of copper sulfate for algae control in certain situations for this reason.

More recently, another chemical algaecide group has become available. These work by either interfering with metabolism or attacking the cell wall. Our product AlgAway uses a quaternary ammonium salt - polyquat, with the chemical name “poly [oxyethylene (dimethylimino) ethylene (dimethylimino) ethylene dichloride]” that works through this mechanism. Used for some time in swimming pools and spas, this chemical has been shown to be safe to use with fish and aquatic plants. The product is shipped at a 60 percent concentration, and must be diluted to 5.4 percent solution before application. Treatment has been very successful at rapidly eliminating most forms of algae, but steps should be taken to reduce the rate of algae growth as the original algae decomposes and returns the nutrients to the water. This can be accomplished by introducing the beneficial bacteria found in AquaClean ACF-32, which will compete with the algae for the available nutrients.

Biological Control

Most biological control agents work in one of three ways. 1) The most common is by competing with the algae for macronutrients. This is especially effective with photosynthetic bacteria, which occupy the same ecological niche as the algae. This mechanism may not be effective in ponds or lakes where there is a high residual nutrient concentration, as there is plenty of nutrients to go around. 2) Some microorganisms, such as Pseudomonads, can also produce antibiotic like compounds that inhibit the growth of algae. 3) Finally, there are some organisms that produce compounds called siderophores that tie up iron, which is essential to the metabolism of algae. Currently, no one has registered a biological algaecides with the EPA, but used in conjunction with a polyquat, like AlgAway, biological treatment with ACF-32 can effectively control algae blooms through nutrient competition.

The major advantage in the use of “biological pesticides” is that they are compatible with the environment and usually exhibit no toxicity for plants, animals or mammals. A study conducted by a graduate student in Ecology at a Midwestern university compared the effectiveness of a biological product containing photosynthetic bacteria to Algae Fix, a commercial pond product containing 4.5% of the polyquat referred to earlier. While shown to be much safer than other algaecides for plants and aquatic fauna some toxicity was still observed, especially to crustaceans, which is noted on the Algae Fix label.

Results on effectiveness of the two products against algae are shown in Graphs 1 and 2. The toxicity results appear in Table 1.

Table 1 – Toxicity of Algae Fix and AquaClean ACF-32

Barley Straw

In recent years, barley straw has gained popularity as an algae control agent. This approach came predominantly from the water gardening market in England where Scottish barley straw bales have been used for years. In this case, barley has been used for years without any real understanding of what the scientific basis for its positive effect. With the increasing popularity of barley straw, various Groups tried to determine whether it’s use was just another “snake oil” remedy, as well as Groups trying to register barley straw as an algaecide, more investigations have been undertaken to determine what if any mechanism is implicated in the control of algae through the use of barley.

What has been determined to date is that as the barley decomposes certain breakdown products are produced including humic and fulvic acids. This makes sense since it normally takes from 4 to 6 weeks to start demonstrating some impact on the barley straw. Both the humic and fulvic acids are strong sequestering agents and have been hypothesized to tie up nutrients. In addition, it has been determined that the breakdown products react with sunlight to release hydrogen peroxide at low concentrations over an extended period of time.

Particulates
Generally particulates are not the kind of logistical problem presented by algae but there can be some relationship. Inorganic particulates will generally only stay suspended when there is turbulence or charge interactions that interfere with normal settling. Isolating the cause of turbulence will usually solve this problem. Some flocculants can also aid in settling but over time inorganic flocculants can build up and cause other problems so a biodegradable flocculant is preferable.

Organic particulates will normally also flocculate out and settle naturally once the organic load in the water is stabilized. The bacteria in the pond can do this but may be sluggish. In these cases, augmenting with organisms that can quickly stabilize the organic load will speed up natural flocculation and lead to naturally clear water.

Recommendations
While it is desirable to minimize algae growth and buildup for both aesthetic and practical reasons, regulatory guidelines and environmental impacts have to be taken into consideration. Addressing the conditions that promote the growth of algae is the first step to take in this effort because it is usually the least expensive and has no adverse environmental ramifications. If you do that, it is feasible to control the conditions that promote algae growth. If the algae bloom is still beyond what is acceptable, then the alternatives discussed above should be considered based on level of urgency, cost and environmental impact.

While a less significant a problem, particulates can be eliminated by settling or filtration, by reducing turbulence where possible, and overcoming charge interactions that may stabilize suspensions of particles and biologically stabilizing the pond.