Pond Maintenance 101
by Casey Coke
by Casey Coke

Casey Coke is a Marketing Manager for Natural Environmental Systems, LLC, a global supplier of microbial solutions for pond and lake management. The company markets their own brand of pond supplies under the registered brand name of Pond Keeper.

August 17, 2008

An Understanding of Water Chemistry, Basic Pond Supplies and Pond Maintenance Routines A little can go a long way. Never has that been truer than in the case of pond maintenance. Sure, every pond is different and there is some very technical and biological information that is very important for the maintenance of a pond. However, being armed with some basic knowledge in a few key areas can be a great start in becoming a confident pond owner, no matter if you own a larger pond like a farm pond or smaller more intensive koi pond or water garden.


You don’t need to be a biologist or chemist to keep your pond water clean and healthy. While undoubtedly having that sort of background helps to understand all of the processes that take place in a pond, a simple crash course in pond water chemistry can go a long way to helping the average pond owner become more knowledgeable and have a successful pond maintenance program.

When people discuss pond water, the most common term used is pH. pH balance is measured on a scale from 1-14 that is based on the concentration of hydrogen ions in the water. A pH of 7 is considered neutral and is the optimal level for a pond and its processes to function optimally. A pH level that is above 7 is considered alkaline and anything below 7 is acidic. The term buffering is used with regards to pH whenever something is introduced into the water that moves the pH from an alkaline level toward the acidic level or vice versa. This can be achieved intentionally through commercial water conditioners or unintentionally through a variety of factors. Some of these contributing factors can be decaying debris and fish waste, fertilizer run-off from grass or nearby fields and even acid rain.

It is these factors above that are usually at the root of most pond problems. Decaying organic matter like grass clippings, dead plants and excess fish food, fish waste and even fertilizer, release nitrogen into the water normally in the form of ammonia, nitrite and nitrate, which can be toxic to fish if the levels get too high. In a biologically balanced pond, the ammonia is turned into nitrite and then eventually nitrate, which is far less toxic and can be used by plants or depleted with a water change.

This decomposing waste, fertilizer and excess fish food also produces a nutrient called phosphate. While phosphate is considered a nutrient and is beneficial to soil, it is not a nutrient that is very beneficial to ponds. In fact, phosphate is the primary culprit behind algae growth. The excess phosphate and nitrogen can quickly cause an algal bloom, which can severely compromise the appearance and the health of a pond.

The primary way that nature combats nitrogen and phosphate is through dissolved oxygen. Dissolved oxygen is the most important factor for a healthy and clean pond. All of the material that falls into a pond that needs to decompose requires oxygen to do so. Dissolved oxygen is also critical for the health of fish, as they require oxygen to process their food. Whenever there is an instance where there are too many fish in a pond or too much decomposing waste, oxygen levels can dramatically drop causing the rise in nitrogen and phosphate leading to fish kills and aggressive algal blooms. It is in these scenarios where oxygenation through aeration is critical, which will be discussed further in the Pond Supplies section.


There are numerous pond supplies and pond products on the market these days. Some pond supplies are critical, while others are merely aesthetic or can be specific to certain environments like koi ponds or water gardens. However, no matter what type of pond you have, there are some pond supplies that everyone should have in their arsenal for a clean, clear pond.


Aeration is key for any pond environment, particularly smaller ponds with lots of fish. As mentioned earlier, fish food and fish waste can lead to increased nitrogen levels, but this is significantly reduced where aeration is provided and dissolved oxygen is introduced to help decay the waste. There are all types of methods of aeration such as fountains, waterfalls, diffused aeration, windmills and paddlewheels. Fountains and waterfalls are very popular pond products because of the visual appeal they bring. However, their effects can be limited based on pond depth. Typically, fountains and waterfalls are best suited for shallow ponds as they generally only oxygenate the top portion of the water column. Because it is crucial that the fountain or waterfall create lots of turbulence at the surface so that the maximum amount of oxygen can be dissolved, fountains that produce a finer mist of water droplets create more turbulence than big droplets and are a better option.

Diffused aerators are the best option for aerating deep ponds. They use compressors to force air, through tubing, to the bottom of the pond, where it is pushed out and upward. They are also excellent choices for pond owners who prefer less surface movement than what you get from fountains and paddlewheels.

Paddlewheels offer similar advantages and disadvantages as the fountains. They typically are best in shallow water environments and not as efficient in deeper water. They are more efficient than fountains and waterfalls at dissolving oxygen due to the agitation effect from the rotating blades.

Depending on the set-up, windmill aerators can be used to oxygenate shallow or deep ponds. They can be set up to work as a diffused aerator and force air to the bottom of the pond, or they can act like a paddlewheel and turn blades that agitate the surface. Seeing as they are wind powered, their advantages and disadvantages are quite obvious. You will save money on electricity, however you lose your oxygenation on non-windy days, which typically occur in the summer when you need it most. Additionally, they are bulky and hard to install, making moving them unrealistic.

Certainly pond depth is important when deciding on the type of aeration to use, but so is the availability of electricity. Ponds without access to electricity may not be able to support a fountain or diffused aerator or the use of electricity to power an aerator may not be in the budget. Fortunately solar technology is allowing fountains and diffused type aerators to be used where normally not possible. Solar panels are used to generate power to 12 V batteries, which in turn supply power to the units. Solar powered systems are available that operate strictly during day- light hours or during both daylight and night hours.


Filtration is largely based on the size of the pond and the number of fish that are present. Typically large ponds like farm ponds or commercial ponds do not require filtration because their size makes it possible for them to naturally filter itself. However it is in the smaller ponds like koi ponds, garden ponds or backyard ponds that filtration becomes highly necessary due to the increased concentration of fish and the smaller water volume.

Choosing a filter system can be challenging as there are many types, however, by understanding the activities in the pond water you can better make an informed decision. Below is information on a few types of filters commonly found at pond supply stores.

Biological filtration is a very popular system, particularly among people who have a lot of pond life. Biological filtration utilizes colony forming beneficial bacteria to break down organic waste and convert toxic chemicals like ammonia to less toxic nitrate. Biological filtration systems utilize filter media as a breeding ground for the bacteria to colonize so that when the water passes through the filter, the attached bacteria can clean the water. Filter media for biological filters come in all shapes and sizes, but as long as the media provides a large amount of surface area for the bacteria to colonize on, it will be fine.

Mechanical filters are relatively cheap options and utilize artificial devices or screens to capture floating debris in the pond. They require more manual labor, as they must be cleaned regularly to remove the trapped debris. Fine screen filters capture a greater amount of waste particles, but clog faster. Due to the generally cost effectiveness of mechanical filters, you may opt to use a series of different sized filters to capture more debris and reduce filter clogs. Mechanical filters are more commonly used in water gardens and ornamental ponds where there is limited aquatic life, as they do not provide chemical breakdown like the biological filters

Chemical filtration utilizes activated carbon to remove chlorine, tastes, odors, colors, pesticides, heavy metals and other impurities from the water. This process is called adsorption, where the waste particles adhere to the surface of the carbon. Chemical filtration is more commonly used in aquariums than ponds, however chemical filtration can be effective in a pond to bridge the gap while the biological filter matures.

An ideal pond filtration system should utilize a couple of different filter methods. Normally pond owners combine a mechanical filter with a biological filter to remove the large waste and then biologically break down the toxins for a more complete water filtration system and a healthier pond.

Beneficial Bacteria

Any pond, large or small, can benefit from the addition of pond bacteria. Beneficial pond bacteria are naturally occurring bacteria that break down organic waste in ponds and convert toxic ammonia to nitrite and eventually nitrate. Beneficial pond bacteria are aerobic, meaning they require oxygen, which is another reason proper aeration is very important. You may be asking yourself, “If they occur naturally, why do I need to add more?’

Well, when waste levels get too high, like in fishponds or farm ponds that get lots of debris, fertilizer run-off or livestock waste, it can be hard for aerobic bacteria to keep up and anaerobic bacteria begin to takeover. Once the oxygen levels drop and the anaerobic bacteria become prevalent, waste is more slowly broken down leading to noxious odors and increasingly harmful levels of ammonia and eventually fish kills

Most every retailer of pond supplies will carry multiple brands of pond bacteria additives that can come in many varieties like liquid, powder, packets and even gels. Some people will add the bacteria directly to the filter media to establish a strong colony in the filter, while most people simply add the product directly to the pond, which allow the bacteria to colonize all over the pond and immediately begin breaking down waste.

The only real concern with adding bacteria is that they are very sensitive to pesticides and herbicides, so it is generally recommended that they not be used in conjunction with chemical products within 48 hours of the application of the chemical. Beneficial pond bacteria is also a key component for follow up after an algaecide treatment to break down the dead algae and help prevent further algae growth.

Water Conditioner

Water conditioners or pond conditioners are chemicals added to water to improve its quality, whether it is for the appearance of the pond water or for the health of the inhabitants. For people who have koi ponds, goldfish ponds, garden ponds or other small ponds with aquatic life, conditioning the water is crucial for the health of the fish. In small water environments, minor changes in water volume, waste and other factors as mentioned earlier can compromise the pH balance and consequently the quality of the water.

Pond supply stores carry all sorts of water conditioners, some of which are multi purpose products that can combine dechlorination and pH buffering with ammonia reduction, electrolyte addition, skin slime coat replacement and flocculation providing a wider range of water treatment. While most of these are great products and are excellent for koi ponds and water gardens, there are other water conditioners more appropriate for large, multi acre ponds.

Large, natural pond owners find it more cost effective to buy bulk products like sodium bicarbonate for pH buffering, calcium carbonate (agricultural lime) or calcium sulfate (agricultural gypsum) to settle mud and clay and sodium thiosulfate pentahydrate crystals to dechlorinate when necessary. These farm pond conditioners may not be found at your neighborhood pond supply store, but a call to your local agriculture agent can quickly get you in touch with a supplier.

While the pond supplies mentioned in this section are just a small percentage of the pond supplies out on the market, they are probably the most crucial pond supplies for a pond owner. They are compatible with each other and enhance each other’s benefits, as well as being compatible with most other pond supplies out there.


Spring Pond Maintenance

Early spring, while the water temps are still below 50 degrees, is an ideal time to evaluate your pond and make plans for the coming season. This is the time for you to take inventory of your pond supplies and make sure you are stocked up on beneficial bacteria, water conditioners and even decide if there were some new things you wanted to try this year like pond dye or maybe barley straw extract.

You should also check your mechanical systems and your pond structures and plan renovations or additions. For instance, farm pond and commercial pond owners should check their spillways for obstructions and the banks for signs of erosions. If banks are eroding and the spillway is clogged, spring rains can cause big problems. Adding vegetation or laying sod on bare banks can help prevent erosion and limit silting. It is also better to find damaged filters and pumps now rather than in the summer when down time could lead to problems. If you are planning to add aeration, now would be the time to put in a fountain or a waterfall to help oxygenate the water, which will be especially important later in the year.

Spring is also a crucial time for your pond because over winter debris and waste that may have accumulated and, due to low water temps, has not decomposed. All of this accumulated waste will begin to deteriorate all at once as the water temps rise, which can negatively effect the water condition. It is imperative that you have your pond supplies at the ready in the form of beneficial bacteria and water conditioners to help offset the decaying waste. Adding bacteria in the early stages of the season is also good because you are giving the bacteria time to colonize on the filter and all over the pond so that when the fish become active and the associated waste do start to breakdown, the bacteria is prepared to handle it.

Summer Pond Maintenance

The summer months are probably the time when most pond issues arise. Warm weather affects dissolved oxygen levels, encourages algae growth and makes fish more active leading to increased feeding and waste production.

Oxygen, oxygen, oxygen…this should be your mantra in the summer. Whatever aeration device is being used, it is imperative that it is operating efficiently and probably 24 hours a day. Warm water does not retain oxygen as well so you need to constantly pump oxygen back into the water. As noted earlier, increased dissolved oxygen levels will help the pond bacteria thrive and improve the reduction of ammonia, nitrites and nitrate, which fuel algae growth and also help fish digest and convert food to energy.

Speaking of algae, the summer months are when algae blooms become commonplace and increasingly hard to control. All types of debris and fertilizer may find their way into the water, plus fish are more active, leading them to feed more often, causing an influx of nutrients. Additionally, more sunlight is penetrating the water fueling photosynthesis within the algae. Generally speaking, limiting available nutrients, reducing sunlight penetration and keeping oxygen levels high is a good protocol for controlling algae. Below are a few ways to achieve this:

• Continue adding pond bacteria regularly to help consume the problem causing nutrients

• Cut back or remove dead or dying plants

• Plant water lilies or other aquatic plants that can shield the water from the sun and also add oxygen to the water. If plants are not your taste try a pond dye to help filter sunlight.

• Check your equipment like filters and pumps to make sure that everything is working well.

Something else that should be done often, particularly in the warmer months, is a pH check. Because so much biological activity is taking place during this time, pH can drastically fluctuate, but regular checks can make sure you catch these swings and can adjust accordingly.

Fall Pond Maintenance

Inside they call it “spring cleaning”. Outside it is called “fall cleaning”. Fall is when you start to do a lot of cleaning up around the pond and prepping it for the winter months. During the fall ponds can become covered in leaf litter, pine needles and grass clippings, all which can cause problems in a pond. Skimming off dead leaves from the surface of the water along with removing leaves and other debris from around the pond’s edge will go a long way in maintaining the water’s integrity. Obviously, size of the pond will determine if this is practical, but if at all possible it should be done.

You will also want to trim back dead or dying foliage from water plants. This will help with the amount of skimming you will have to do. Along these same lines, if you have any non-hardy plants in your pond, now is the time to re-pot them and move them inside for the duration of the fall and winter.

Because water temps are starting to fall, the amount of food the fish need is reduced, therefore you should reduce the amount of food you feed them. Water temperature affects a fish’s metabolic rate and as water cools, their metabolism slows. If you continue to feed them at the rate you did in the summer, you will create excess waste and bottom sludge or even worse kill them.

Of course, like the rest of the year, continue with your regular beneficial bacteria applications and check your equipment and structures for damage or clogs to ensure everything is operating well.

Winter Pond Maintenance (Pond Winterization)

Based on where you live, the winter months can mean more pond maintenance for some and very little for others. Generally during the winter there is not much to do if you have done the proper maintenance in the fall, as far as cleaning in and around your ponds and checking your equipment. As the water gets cold, the fish require virtually no food, as they are extremely inactive. Additionally, cooler water retains dissolved oxygen better meaning oxygen is not as critical as in the summer. However, in areas where temps get low enough to freeze over a pond, there are some things that need to be done to ensure your pond and its inhabitants survive the winter.

Probably the most important thing to remember is to not let the pond freeze over completely. If the pond surface completely freezes over, then the gases that are produced during decomposition of debris cannot escape and can pollute the water. Also, if the toxic gases cannot get out, then that means oxygen cannot get in, which of course is a problem. An easy solution to this is the use of a de-icer. De-icers are just that, devices used to thaw ice from the surface of a pond. They are not meant to thaw an entire pond, but just a small area so that oxygen transfer can occur. Generally they are placed in the shallow part of the pond. Depending on the size and ice accumulation in a pond, sometimes two de-icers may be needed.

Some people recommend aeration as a means of keeping the pond from freezing over, because moving water, like from a fountain or waterfall, is hard to freeze. The drawback to this is the fact that the aeration unit can cause hyper-cooling, meaning additional cooling of the pond water. If using an aerator in the winter, it is advisable not to use one that pumps air from the bottom of the pond. This can stir sediment causing unnecessary stress on fish, as they tend to stay near the bottom where the water is most warm. It is also recommended that you either insulate or keep the pump indoors so that the water being pumped in will be slightly warmer when pushed back out and will not further cool the water.

During the winter months it is not that crucial to continue with the regular maintenance doses of bacteria, as the bacteria become pretty inactive in the cold water. However, at least one dose throughout the winter can be helpful for the early spring warm-up by giving you a bit of a head start.


If you are a new pond owner it can seem a little overwhelming thinking about trying to keep that pond clean, clear and healthy. You see all of the pond supplies out there and all of the technical terminology and your head can spin. But, if you just remember to aerate and filter the water, supplement with beneficial bacteria and check the pH regularly to determine if any water conditioners are needed, you will be off to a good start and will find you have given yourself a strong foundation to build on.

Casey Coke is a Marketing Manager for Natural Environmental Systems, LLC, a global supplier of microbial solutions for pond and lake management. The company markets their own brand of pond supplies under the registered brand name of Pond Keeper.

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