IBN has a few pond management articles that may be of interest to pond owners. No fluff, no sales pitch, just information
Successful long-term pond and lake management requires a “Holistic Approach”. Holistic Management is an objective driven means of manipulating aquatic ecosystems using environmentally responsible materials. Holistic pond management involves accessing the factors that are occurring within the pond and using this information to implement the most appropriate management program. The three primary tools are aeration, beneficial microbes and physical removal. In this article, we will briefly review the three components and their use in pond and lake systems.
Aeration provides a life-giving breeze within the pond. Of the available types, bottom diffused aeration provides the most efficient operation in ponds deeper than 8 feet deep. Oxidation of bottom material accelerates decomposition, reduces production of hydrogen sulfide gas, and reduces the amount of black material on the bottom. Also, decomposition is highly accelerated (20-30 times faster) under aerobic conditions. Aeration also provides movement within the pond. Finally, aeration disrupts the thermocline, permitting fish to inhabit deeper waters. Some concern arises that the cooler layers of the pond will no longer be available for the fish to use. However, under periods of anoxia (no oxygen), the fish are not able to tolerate the low dissolved oxygen levels in the cooler layers. In most cases, fish will be better served to provide them with more area to inhabit rather than being concerned with disrupting the temperature profiles.
Beneficial microbes or bacteria are a formulated blend of organisms designed to consume reactive nutrients and organic muck. These blends contain additional micronutrients and enzymes that enhance the natural process already occurring within your pond. In some situations, the microbes can actually enhance the transfer of nutrients to your fish by optimizing the food chain. An intact food chain allows more efficient transfer of nutrients up the food chain. For those who are fertilizing your lakes to obtain optimal production, the use of beneficial microbes can decrease the amount of fertilizers needed.
Here’s how: much of the fish waste, dead algae, tree leaves, etc. accumulate on the bottom of your pond. This represents a large sink of nutrients that are mostly unavailable for fish growth in a short time frame (growing season). Adding beneficial microbes can convert much of this organic material into more usable forms that are consumed by rotifers, daphnia, and protozoan. The result is less fertilizer added and more fish production.
By removing debris from the pond you are removing nutrients for potential future growth. Every bit of debris you can remove from the pond is going to help you in the long run. Therefore, it is well worth you time to consider raking your pond. Removal of leaves, blown in debris, and dead and decaying plant material will substantially help to reduce the amount of nutrients into the pond.
Each of the three primary components within holistic management (bottom diffused aeration, physical removal, and beneficial microbes) plays a role in proper pond management. When used in conjunction, these tools allow holistically aware managers the ability to establish a healthy water resource. Although seemingly simplistic, it is important to realize that just tossing these materials into a pond will not necessarily solve all of the problems. Also, the order in which these materials are used in the pond is also critical. Age, nutrient loads, and organisms influence the management implemented. Therefore, experience and a strong ecological background are necessary to optimize the effectiveness of this management approach.
So, how do I properly maintain my pond?
Set goals & objectives for your pond. Do some research and determine the feasibility of your goals and the time required to reach the desired outcome. You can never reach your goals if you don’t set any.
It is important to realize that no magic bullet exists when managing a pond. With such a diverse system, it is nearly impossible to find a single solution that positively influences every component of the system. Therefore, management must consist of several components that work in conjunction to promote a healthier system.
Determine the cause of your problem. Dense, filamentous algae is not the problem of a poorly managed pond, it is only the symptom of an underlying problem. Nutrients that have accumulated within your pond are the problem. This extends to managing your fish as well. Stunted bass is not the problem but a symptom of poor environmental conditions, limited forage, etc
NUTRIENTS. You must manage nutrients. Nutrients can be you friend or foe depending on your goals. This could require changes in the nutrient ratios for fish production or the physical removal of debris for swimming ponds. Regardless of your objectives, nutrients are the driving force and must be properly managed according to your goals.
Get sound advice. Although the above principles seem straight forward, there are many technical and ecological factors that influence the effectiveness of holistic management. A quick analogy: essentially, your pond can be equated to a city; many individuals each performing their own job, yet influencing other individuals. Now, try to keep the city functioning without any major difficulties. It can become difficult to make sure everyone is doing his job and keeping things in order. The same is true for managing your pond.
A final thought, it has likely taken several years for your pond to develop problematic growth. It is important to realize that holistic management will not correct pond problems in just a couple of days. However, as the system becomes more balanced, you will see changes occurring. In the long term, the system will improve and will not have the problematic algae growth that had once plagued the system. Keep these holistic principles in mind and you’ll be on the right track to a balanced pond.
Holistic pond management provides the basis for Inspired By Nature’s all natural pond management. Holistic management is the process of determining the underlying causes of pond problems and developing best management practices to solve the problems. Bottom diffused aeration provides effective means of managing the pond’s ecosystem. Another component, microbial application, proves to be effective in controlling water quality problems. At the same time, it holds the potential to increase fish production within the pond.
What exactly are “Beneficial Microbes”?
Microbes or bacteria are small, single-celled organisms that occur in practically all conditions imaginable. Many are aerobic, requiring oxygen to survive. However, a number of bacteria are capable of surviving in the absence of oxygen. Although variously shaped, they are typically round or rod shaped. These organisms are so small that they cannot be seen with the naked eye. In fact, approximately 8,700,000 round rod-shaped bacteria cells could be contained in the period at the end of this sentence. With few exceptions, microbes’ primary role is that of decomposers, consuming organic muck and dead material and allowing it to be used within the system. In fact, without bacterial decomposition, your pond would fill with dead material very quickly.
Like all other living organisms, bacteria need to eat to survive. To feed, per say, bacteria absorb nutrients that are available within their surrounding area. To facilitate this decomposition, bacteria actually release enzymes that allow for the breakdown of tissue (animal or plant) externally. As the dead tissue breaks down, their components are absorbed and made available for the growth of the bacteria, which are then followed by assimilation of this material into the cell.
Another aspect of microbial growth is that of a boom and bust growth pattern. Somewhat similar to an algal bloom, microbe populations tend to grow and reproduce very rapidly, and are then subject to a crash in the population as their food sources are depleted. Implications…following initial introductions of the microbes, microbe growth will be very rapid, producing an exponential growth of the population. Under these conditions, the microbial population can double from every 20 minutes to up to every 8 hours. The result, rapid growth and rapid consumption of both reactive nutrients and organic sludge. Microbes, like your fish, consume oxygen. Therefore, an aeration system may be necessary as a result of the rapid respiration that results from the initial microbial growth in older ponds.
Role of Beneficial Microbes in Your Pond
Research has shown the importance of microbes within aquatic ecosystems. Referred to as “The Microbial Loop,” this process emphasizes the role that bacteria play in transferring energy within aquatic systems. Traditional food chain theory emphasizes the role that primary producers(algae), primary consumers(zooplankton), and secondary consumers (small fish). In the background, however, are the decomposers. Although sometimes overlooked, these organisms play a critical role in any food web.
Typically, microbes are seen only for the role they play in decomposition, allowing for the recycling of nutrients, making them available for future plant and animal growth. However, they also play an important role in transferring energy to the primary consumers such as the zooplankton. The result, utilization of energy from the decomposition of organic decay in addition to that of photosynthesis by primary producers.
Within every pond there are billions upon billions of microbes. In fact, there are microbial populations established in nearly every aquatic environment. The key, however, lies in the diversity of the microbes that are present.
Each microbe plays a slightly different role or niche, that allows for efficient decomposition of organic matter within the system. In addition to the microbes, enzymes are added to the mix. The enzymes enhance the natural role of bacteria, allowing for more rapid mobilization of the nutrients within organic matter (sludge).
Now, this may seem somewhat contradictory to our goal of managing excessive nutrients. Why would I want to mobilize nutrients that are tied up in the sludge at the bottom of my pond? Number one, efficient decomposition of this sludge will permit you to actually increase the depth of the pond. Number two, the decomposition of the material will allow those nutrients that are piling up in your pond bottom to become available for fish growth. In addition, fewer nutrients are available for algae growth in the water column.
As previously stated, algae are the base of the aquatic food chain. This large food source is consumable by small organisms such as daphnia and copepods, which are in turn consumed by small fish. However, bacteria can also play an important role in this food web. Many of the small filter-feeding organisms that consume algae are also able to consume bacteria. This can be especially important in situations where filamentous or other algae inedible to zooplankton are present. This has the potential of converting inedible food sources into fish biomass via microbial consumption. At the same time, a transformation of nuisance algae into more consumable bacteria shows improvements in water quality as well as holding the potential for increasing fish growth.
When used with Inspired By Nature’s other holistic management approaches such as periphytic filtration and bottom diffused aeration, microbial enhancements can produce outstanding results in water clarity and reduction of organic sludge. At the same time, we can also enhance fisheries by providing an edible food source for many of the zooplankton and protozoans within the pond.
Aeration is an important part of many lake management and restoration efforts. Naturally, most ponds will undergo two stratification periods annually. Stratification creates two distinct layers of water that are separated by a transitional layer (thermocline). Because of the density differences between the layers, the lower layer (hypolimnion) is isolated from nearly all input of atmospheric oxygen while stratification persists.
Without aeration, many ponds will develop an oxygen-deprived hypolimnion throughout the summer. The same ponds may also run the risk of oxygen depletion under periods of extended ice cover. Ponds that undergo periods of oxygen depletion may be influenced to different degrees ranging from a decline in ecosystem efficiency to the extreme of experiencing episodes of fish kills. By disrupting the pond's stratification, the pond's ecosystem is supplied with adequate oxygen, preventing the suffocating effect that would have otherwise occurred.
Aeration is also an important tool for reducing the accumulation of organic muck that builds up on the pond bottom. Under low oxygen conditions, decomposition takes place at a much slower rate than under oxygenated conditions. As a result, organic material is decomposed at a very slow rate, in fact, usually slower than the rate that new organic material is being created. The end result...a pond that is rapidly becoming shallower as it fills with organic material.
Simultaneously, gases bubble up from the muck, producing the foul rotten egg smell. Proper aeration can actually reverse the build-up of organics in the short-term (natural succession dictates that a pond will naturally fill in) and eliminate the foul odors as a result of the accelerated decomposition of organic material under oxygenated conditions.
Aeration is also instrumental in managing nutrients. Under anaerobic conditions, phosphorous compounds become soluble allowing the phosphorous to be assimilated by other organisms (i.e. Algae). However, by maintaining an adequate supply of oxygen it can be retained in the sediments where it is unavailable for algae growth.
What types of aeration are available?
Although there are many variations in the types of aeration systems available, most can be classified as either surface or bottom aeration. Surface aeration systems, such as fountains and agitators, work by pumping water into the air or by mixing surface water. These surface aerators can operate effectively in ponds less than eight feet deep, but are typically
ineffective at aerating deeper bodies of water. Efficiency is also sacrificed in fountain systems as a result of having to pump water into the air. Maintenance also tends to be higher on these units and issues of safety arise with the need to run electric lines through the water. Although the fountains may be aesthetically pleasing, owners must also deal
with the inconvenience of the floating unit, which may restrict water usage in certain situations.
Bottom aeration is the second category of aeration devices. Although design and materials vary, most bottom aerators incorporate the same principle; releasing compressed air or oxygen through a diffuser located near the bottom of the pond (use of pure oxygen is not usually practical or necessary in most pond situations). The greatest advantage of bottom aeration over other types is that the positioning of the aerator allows for the oxygenation of the entire water column. As the bubble plume rises through the water column, it also moves a column of water with it. This water movement disrupts the stratification and creates uniform oxygen concentrations throughout the pond. In addition, bottom aerators operate
efficiently, present few safety hazards, and pose little concern for water recreation.
The critical difference between bottom aerators arises from the type of diffuser used. Much emphasis is placed on the efficiency at which oxygen from the air bubbles diffuses into the water column. Although an important consideration in some aquatic applications, it is not a great concern for pond management. However, it is important to note that smaller diameter bubbles produce better oxygen diffusion, but more importantly, move a greater volume of water within the bubble plume. By maximizing water circulation within the pond, the oxygen that diffuses into the upper layer of the pond from the atmosphere and from photosynthesis, gets mixed with the anaerobic waters in the hypolimnion. The result is a
uniformly aerated pond that is operating efficiently and is aesthetically pleasing.
Proper aeration can make considerable improvements in a pond ecosystem. By circulating water within the pond, stratification is eliminated and dissolved oxygen levels rebound. Higher oxygen levels yield greater biotic growth, including fish growth. However, aeration is just one of the tools needed for holistic pond management. To maintain a balanced ecosystem, other tools including beneficial microbes and physical removal need to be used in conjunction with aeration. Implementing this multi-faceted approach allows managers to work with Mother Nature to meet their goals.
At Inspired by Nature, Inc., we are always getting questions about fish management and stocking. As you may know, our answer is usually in the form of another question, “What are your goals for the pond?” As you decide what types of fish you may want to stock, here are a few pointers.
First, my most often asked question… “How many more grass carp should I add to my pond? I just can’t get them to control the stringy mat algae on the surface.” Actually, you can add about as many as you want, they still will not control the filamentous mat algae. Grass carp are selective eaters, first consuming desirable rooted vegetation prior to even considering the consumption of algae. In fact, they’ll beach themselves on the side of your pond to grab a bite of lawn long before they’ll eat the algae. Does this make grass carp useless for pond management? Absolutely not, they can provide long-term control of rooted vegetation provided that proper numbers are stocked for the type of plant material that you have. Remember, that grass carp prefer to eat grassy material, if you do not have rooted plants in your pond, they will have nothing to eat. No food equals no fish. No fish equals wasted money! Therefore, do not stock white amur for preventative purposes. It is best to stock them as soon as you see that the vegetation is getting slightly out of control (greater than 20% of the pond area). If you’re not sure what type of plant you have, send IBN a sample and we’ll be glad to assess what needs to be done.
“Where can I get these so-called super hybrid bluegill?” Many pond owners are convinced that they need to have hybrid bluegill in their ponds. They grow fast, taste great, and they get to lunker sizes (supposedly up to 3 ¾ pounds). What could be wrong with that? Nothing, if you can prevent them from reproducing in your pond. The hybrid bluegill is a cross between a bluegill and a green sunfish. This produces a viable (NOT STERILE) cross.
Hybrid bluegill will reproduce within your pond! If you’re told differently, you’re being lied to. The catch is that their offspring will usually be about 90% male and 10% female. This will limit reproduction, but will by no means stop it. This is especially true if you have also stocked pure bred bluegill at the same time given that these should be nearer a 50:50 ratio male to female. This provides an abundance of fertile females for the 90% male blue-green sunfish population to reproduce with. Okay, so the hybrid bluegill will reproduce between themselves and with the pure bluegill in the pond. Now for the kicker. Genetics will prove to you that when hybrid bluegill reproduce, their offspring will revert back to either bluegill or green sunfish. For those of you with a pond full of green sunfish, you can contest to the problems that they cause. Nipping, stunting, and competition with largemouth bass are just a few of their traits.
Catfish have their place in many ponds, but make sure that your pond is one of them. Catfish grow fast, are easily pellet trained, and can survive about any condition you throw at them. If you’re a huge fan of catfish fillets, stock them! If you’re indifferent, I’d probably not stock them. Many people are under the belief that catfish only eat rotted bottom materials and work to keep the pond bottom clean. Would you eat the black muck at the bottom of your pond? Catfish will in fact eat dead fish and other bottom insects, crustaceans and Catfish have their place in many ponds, but make sure that your pond is one of I’ve also seen them consume the occasional duck and baby goose. One thing many people don’t consider is that catfish also eat fair amounts of bluegill during the night, creating competition with your largemouth bass. If you do decide to stock and harvest catfish, remember that catfish rarely reproduce in smaller impoundments. Therefore stock what you catch to replace those harvested.
And my favorite… common carp, golfish, and koi. During a typical season I see 20-30 ponds that are completely overrun with at least one of these three species. The common carp (Cyprinus carpio) and koi (Cyprinus carpio) are actually the same fish species, with koi being highly domesticated and bred for their ornate color. Goldfish are a separate species but with similar characteristics. These fish are highly reproductive and if only a few predators are present, will fill your pond quickly. So what’s the problem with a bunch of colorful goldfish swimming around my pond? Hungry goldfish, carp, and koi will root around in the bottom and create water clarity problems, especially if you have a clay or silt bottom. Best of all, any of these three species will gladly hybridize with each other. So, if you think you’ll add one of each to prevent them from reproducing, you’ll be sadly mistaken. A little example: I performed a fish kill on a 1/3 acre pond that had approximately six 4-inch goldfish originally stocked 4 years prior. At the time of the fish kill, the was brown, muddy, and had a clarity of 5 inches. After two days of netting dead goldfish, we had accumulated over 175 pounds of goldfish from a shallow 1/3 acre pond. Yes, 175 pounds in a small, shallow pond, all from 6 original fish! Granted, there were no predators in this system, but you can see the potential for problems that these guys possess.
And finally, how do undesirable fish such as goldfish, carp, and green sunfish end up in my pond? As far as I am aware, there is still no such thing as spontaneous generation. Birds rarely transport fish or fish eggs from pond to pond. So what’s left? The neighborhood kids, fishermen’s bait buckets, and “contaminated” fish stockings. The biggest culprit, however, is the most easily prevented. Many pond owners rely on ditch or creek water to fill or maintain the water levels in their pond. In doing so, many fish, insects, snails, and leeches are pumped directly into your pond. And believe it or not, many of these fish survive the ordeal with little or no harm. My suggestion, if your going to pump water into your pond, get yourself a filter sock (IBN carries these by the way). The filter socks are a small investment to protect the health of your fishery.
As you can imagine, there are no black and white rules for managing fish in your pond. The above fish recommendations can, however, make achieving the goals for you pond much easier. With our move to our spacious new location, we now have the facilities to provide a full line of fish for your pond stocking needs. If you have any questions about stocking rates or which fish species to stock, call and talk with a biologist to decide what fish will work best for your pond.
Sunfish are undisputedly one of the most popular fish for ponds and small lakes. Sunfish encompass a wide variety of fish including bluegill, redear sunfish, green sunfish, hybrid bluegill, pumpkinseed, and even largemouth bass. This fact sheet will discuss the two primary prey species, bluegill and redear sunfish. Sunfish are well adapted to pond life and provide a sustained forage base for larger predators. They also offer excellent recreational and table fare opportunities.
When stocking sunfish, or any forage fish for that matter, it is essential to stock a predatory fish (for example Largemouth Bass). In the absence of predators, sunfish will reproduce to such a rate that your pond will become overrun with small, malnourished fish. This situation referred to as “stunting” produces poor fishing conditions and an imbalance in the fish population.
Also, when it comes to stocking any sunfish, it is very important to ensure that you are in fact stocking the sunfish species that you desire. Most sunfish have similar characteristics, sometimes making identification difficult. However, many are quite different in habitat usage and temperament. Therefore, haphazardly stocking sunfish into your pond can create many headaches in the future. Take the green sunfish for example. Superficially, they resemble a bluegill. However, if a sizable population of green sunfish becomes established in your pond, you can usually expect small fish size and very aggressive fish that bite swimmers.
Bluegill (Lepomis macrochirus)
Bluegill are the most popular and best suited sunfish for fishing ponds. Pure bred bluegill have a very small mouth with an upper jaw that does not typically extend to the front of the eye. Their opercle (gill flap) is flexible and the bluegill have a long, moderately pointed pectoral fin. There is also a dusky spot on the webbing of last three fin rays on dorsal fin. Two bars extend back from the mouth and chin, and the lower end of gill cover is bluish, hence the name bluegill. There are 5-9 double bars on their sides with young bluegill having a few, large spots on their breast. By fall, bluegill will reach 1.0” to 4.0”with adult bluegill reaching sizes of 3.5” –10.0”. In regard to habitat, bluegills are most abundant where suspended clays and silts are absent and vegetation present. Their preferred spawning habitats are bottoms consisting of sand, gravel or muck. Bluegills will spawn several times throughout the summer, providing considerable forage for predatory fish.
Redear Sunfish (Lepomis microlophus)
Redear Sunfish have proven to be an excellent addition to the fisheries of many ponds and lakes. A relative of the Bluegill, the Redear sunfish is similar in shape and size. Redear are most easily recognized by the red spot on the back side of opercle (gill cover) on males. This spot is orange in females. They also have long pointed pectoral fins and dorsal and anal fins without definite spots. Juveniles can reach 3.0” by fall with adults reaching 4.5” to 9.0”.
Differences between bluegill and redear arise when comparing the habitat and feeding requirements of the two. First of all, Redear sunfish are very structure oriented, unlike their Bluegill counterparts who will frequent open waters. Like bluegill, redear sunfish consume small aquatic insects. However, snails and other mollusks comprise a large portion of the Redear’s diet. Although both species will inhabit sand and gravel beach areas during their spawning season, Redear sunfish usually reproduce only once per season, reducing the time they will be in the beach area.
The reduced spawning that is characteristic of the redear also enhances their role in some pond and lake ecosystems. These systems include ponds used primarily for swimming, where fishing is of low priority. However, it should be noted that having redear as the only forage in a pond will not support a very large predator population. To enhance the predator’s growth, additional forage such as fathead minnows must be added if a healthy predator population is desired.
Both Bluegill and Redear sunfish can be stocked within the same fishing pond. In fact, these species are able to cross or hybridize with each other. The hybrid of a bluegill and Redear sunfish show excellent hybrid vigor, meaning that the next generation of fish grow faster and are more desirable than the parent species. Hybridization of these species will be more pronounced in ponds with limited water clarity.
Sunfish are the base of most farm pond fisheries. With their tolerance small, shallow waters, as well as their desirability for fishing and consumption, they are a great addition to most any pond. Please contact Inspired by Nature, Inc with further questions or stocking recommendations for your pond.
Trautman, M.B. 1981. The Fishes of Ohio. The Ohio State University Press. 782 pp.
Copper sulfate and other derivatives of copper have been used to control undesirable algae in lakes and ponds. Application consists of spreading copper sulfate crystals or powder along problematic areas, or spraying a slurry across the water surface. In most instances, copper sulfate is very effective in killing the floating mats of algae; unfortunately, such control of algae is of very short duration. On the contrary, the negative impacts of the copper sulfate are long term.
Following application of the copper salt, reactive copper concentrations become elevated and remain so for about two hours. The active copper ions are attracted to carbonate ions and become strongly bound. This new compound of copper carbonate drops out of the water column and binds up the copper. The result is that the copper is only effective at killing algae for only two hours. Button et al. (1977) performed copper experiments in Columbus, Ohio ponds, demonstrating that within two hours, the copper concentrations returned to pretreatment levels. After this period, only the algae exposed to the copper for the 2 hour time period may die. However, new algae already begin to grow following the precipitation of the copper. To add to this, the alga that has been killed is releasing nutrients, spurring new growth.
Besides promoting algae growth as a result of nutrient recycling, copper sulfate kills tiny beneficial animals that filter algae from the water column. Doses of copper sulfate required to kill algae are 10 to 100 times that required to kill these beneficial zooplankton (Cooke and Kennedy 2001). The result is increased planktonic algae growth with every copper sulfate application. Cooke and Kennedy affirm this reporting that “very low levels of copper are toxic to algae-grazing zooplankton, leading to a ‘rebound’ of algal biomass as copper is removed from the water column by precipitation within hours of application.”
For drinking water ponds, there is also concern of the copper-induced release of toxins from blue-green algae. Specific types of algae produce toxins harmful to humans and pets. These toxins can cause gastrointestinal distress, liver failure, and even death (Hitzfeld et al. 2000). Bluegreen algae blooms are more prevalent in ponds without algae-grazing zooplankton, a situation that can result from copper treatments (Cooke and Kennedy 2001). Copper sulfate has also caused species of bluegreen algae cells to lyse, causing the release of hepatotoxins into the water column (Lam et al. 1995). Because typical water treatment methods have limited ability to remove these toxins, preventing the growth of these algae is key.
Finally, copper sulfate negatively affects the benthic community in lakes and ponds. The rapid precipitation of the copper ions causes the accumulation of the copper in the bottom sediments. At this point, the copper reduces the diversity of benthic organisms that maintain the aquatic ecosystem. Most importantly, benthic microbe (bacteria) growth is inhibited by elevated copper concentrations. Without microbes, dead organic material accumulates on the pond bottom, causing a rapid filling of the pond. Without the use of copper, microbes will thrive on the dead organic material and will slow the filling process of the pond.
Copper sulfate has historically provided a quick fix for algae problems in lakes and ponds. Unfortunately, the long-term side-effects outweigh the short-lived benefits. While attempting to make ponds more aesthetically pleasing, the balance of the ecosystem is skewed, pond filling accelerates, and the possibility of algae toxicity increases. The best solution for excessive algae is to eliminate copper usage and to adopt a Holistic Approach. This approach includes aeration, microbial augmentation, and physical removal.
Button, K.S., H.P. Hostetter, and D.M. Mair. 1977. Copper dispersal in a water supply reservoir. Wat. Res. 11:539-544.
Cooke, G.D. and R.H. Kennedy. 2001. Managing drinking water supplies. Lake and Reserv. Manage. 17(3):157-174
Hitzfeld, B.C., S.J.Hoger, and D.R. Dietrich. 2000. Cyanobacterial toxins: Removal during drinking water treatment, and human risk assessment. Environ. Health Perspectives 108: 113-122.
Lam, A. K-Y., E.E. Prepas, D. Spink, and S.E. Hrudey. 1995. Chemical control of hepatotoxic phytoplankton blooms: Implications for human health. Water Res. 29:1845-1854.