An ecosystem pond closely resembles a natural habitat. Hobbyists who prefer this type of pond focus on biological filtration systems instead of relying on chemicals and equipment. These ponds are designed to attract friendly wildlife and promote a diverse botanical environment, highlighting features of the pond that mirror a natural ecosystem.
Building an Ecosystem Pond
Location
The best area for an ecosystem pond is one that receives a combination of light and shade, ideally between three and six hours of direct sun exposure each day. Too much sunlight can lead to excessive algae growth, higher water temperatures, and reduced oxygen levels, while too little can hinder the photosynthesis necessary for plant growth. It’s also important to note that koi are cold-blooded fish and depend on their environment to regulate their body temperature.
Most residential building codes prohibit the construction of ponds in front yards, which is why koi and goldfish ponds are typically found behind homes. If your yard has slopes, it’s best to build your pond at the highest point. This is important because leaves, fertilizers, and other surface runoff can block sunlight and disrupt the water’s balance. Since runoff collects in low areas of the yard, these spots are usually the least suitable for installing an ecosystem pond.
If your pond is located near trees, it’s important to know how far their root systems will expand. Tree roots naturally seek out water and can damage the pond liner as they grow. It’s important to note that cutting into a tree’s root system can ultimately kill the tree and should be avoided. A general guideline is to multiply the trunk’s diameter (in inches) by 1.5 to determine a safe radius to start your pond. This can vary based on the type of tree, so research the specific root systems of the trees in your area.
Shape
The shape of a pond can influence waste accumulation, ease of maintenance, and water volume. Complex pond shapes can disrupt or slow circulation, which may lead to waste buildup and negatively impact water quality. Unfiltered waste and decomposing organic matter can increase ammonia and nitrite levels, posing hazards to fish. For these reasons, a simple pond design is generally preferable for ecosystem ponds.
Contours are also important when designing your ecosystem pond. Rounding the bottom and sloping from the sides to the center will help the water circulate waste. Sloping to this area makes cleaning much smoother and facilitates better water parameters. Also, if your pond is in a climate where freezing occurs during winter, sloped sides will push ice upward instead of against the pond, putting less stress on the liner.
Size
The ideal depth for your pond varies based on your environment, but most ponds should be between four and six feet deep. If your area experiences significant temperature fluctuations, it’s best to dig deeper. Shallow ponds are suitable only in climates where temperatures do not change significantly between seasons. Additionally, deeper ponds protect your koi by making it more challenging for land-based predators to hunt them.
One of the most common problems pond owners face is overstocking. The desire for more koi and goldfish is inevitable, but your pond needs to stay within healthy limits. A koi pond should contain at least 1,000 gallons for the first fish. Allow no more than one mature koi or three mature goldfish per each additional 200 gallons of water.
Biological Filtration
Every pond requires biological filtration to maintain proper water quality. Beneficial bacteria break down waste products into less harmful substances by converting ammonia and nitrites into nitrates. These bacteria need surfaces they can attach to, such as sand or rocks. Or, you can add a biofilter to your pond, which helps convert harmful waste to carbon dioxide that aquatic plants can convert to supplemental oxygen.
Bog Filter
Pond owners who want to keep their ecosystems as natural as possible often opt for bog filters. This setup uses pipes to pump water from the pond through a muddy area laden with a substrate such as pea gravel. When waste-filled water from the main pond moves through the substrate, bacteria convert it into nitrates that plants can use for fuel. You can set your bog apart from the main pond by raising or partitioning it. Bog filters should be shallow to avoid low-flow areas. About one foot deep is suitable in most cases.
Plants
Aquatic plants are essential to a pond’s ecosystem. They supply oxygen, food, and shelter for fish and other species that share the habitat. Pond plants are classified into three main categories: floating, shallow, and submerged. A healthy ecosystem usually requires a balance of all three types.
Floating plants rest on the surface of the water, providing shade and shelter. Their roots absorb nutrients that help control algae growth, preventing overpopulation. Some of the most popular floating plants include water lilies, water hyacinths, lotus flowers, water lettuce, and poppies. These plants are easy to install and require minimal maintenance as long as water temperatures remain above 60 degrees. If you live in a colder climate, you’ll need to bring these plants indoors during the winter. The floating plants most vulnerable to freezing are water hyacinths, water lettuce, and ferns.
Shallow-water marsh plants typically grow along the edges of ponds in just a few inches of water. They provide a natural appearance while enhancing the pond’s filtration system, increasing oxygen levels in the water, and attracting insects that koi eat. These plants require consistently moist soil and need some soil coverage over their roots. Some popular shallow-water plants include water iris, lilies, lotus, umbrella plants, and horsetail.
Submerged plants grow entirely underwater. These plants effectively remove toxins and excess nutrients from the water while providing beneficial oxygen. They require grounding into the soil or substrate at the pond’s bottom, or you can grow them in anchored pots. Ensure enough space between the plants for growth and adequate water flow, and trim if necessary. Popular submerged plants include fanwort, elodea, foxtail, and purslane.
Oxygen is just as essential underwater as it is above, and aquatic life cannot survive without it. Pond plants function much like terrestrial plants by absorbing carbon dioxide during photosynthesis and releasing oxygen as a vital byproduct. Fish breathe in oxygen through their gills and release carbon dioxide. Koi and goldfish require at least 5.0 ppm of dissolved oxygen for normal breathing while at rest.
Rocks & Gravel
Rocks and gravel are essential elements of an ecosystem pond. Beneficial bacteria adhere to these materials, consuming excess nutrients and waste in the water, which helps to control algae growth. It’s important to place rocks and gravel on all horizontal surfaces in your pond, including shelves. While maintaining cleanliness may require a bit more effort, an ecosystem pond will accumulate muck at a much slower rate than a traditional pond.
A substrate is well-suited to koi’s natural bottom-feeding habits. Constructing a gravel layer at the bottom of the pond creates an environment where koi can forage for leftover food particles and edible algae. Additionally, rocks and gravel offer shaded areas beneath the pond’s surface, helping to regulate water temperature during hot seasons and providing shelter from predators.
Choose smooth, rounded rocks and gravel to minimize the risk of injury to your koi. Pay attention to the size of the stones and gravel as well. If the gravel is too fine, koi may accidentally ingest it while foraging. Additionally, the small crevices between particles can harbor harmful bacteria. On the other hand, if the rocks are too large, they may be difficult for koi to navigate through. It’s also important to ensure that the stones you select are chemically safe for koi.
Consider using pond rocks with sloping edges around the perimeter of an ecosystem pond. This design mimics the natural banks of ponds and streams. Angled pond rocks with moss-filled crevices will attract frogs, salamanders, insects, and other wildlife to your pond.
Wildlife
Your ecosystem pond will attract various wildlife, some good and some bad. Four types of wildlife cohabitate or visit ponds: mammals, birds, reptiles, amphibians, and invertebrates.
Mammals
The most likely mammals to visit the pond are also among its biggest threats: raccoons, minks, and weasels. Raccoons are found throughout the United States and thrive in part due to the food sources they find in homeowners’ yards. These opportunistic animals will eat almost anything, including the fish in your pond. Minks and weasels, while less common, are found in most of the U.S., primarily near dense forests, coastal marshes, and swamps. They are more dangerous than raccoons, as they are aggressive hunters.
Birds
Creating a pond can attract a variety of birds, which is often a positive aspect. Watching songbirds can be a delightful experience, as they are captivating and their melodies add charm to your surroundings. However, the presence of these small, harmless birds can also invite predatory birds that pose a significant threat to your pond’s fish. Certain birds of prey can eliminate all the fish in your pond in a matter of minutes. The most common ones to protect your pond against include hawks, ospreys, herons, kingfishers, and cormorants.
Reptiles
Turtles are the most common reptiles you are likely to encounter in an ecosystem pond. They play a beneficial role by consuming dead plant matter, which helps maintain healthy water conditions. While most turtles are scavengers, snapping turtles may occasionally eat goldfish or juvenile koi. Additionally, certain snake species found near water may consume koi eggs and fry, as well as small goldfish.
Amphibians
Many koi pond owners appreciate having frogs or toads in their ponds. These amphibians can consume up to 10,000 insects in a single summer season. Additionally, they help clean the pond by eating excess algae and organic materials. Most frog species coexist well with koi, with the exception of bullfrogs.
Insects
Insects are the most common invertebrates found in a backyard pond. Your koi will likely encounter mosquitoes, mayflies, dragonflies, water striders, midges, and more. Maintaining clean water, good water parameters, and a well-functioning filtration system will help keep their numbers manageable, allowing koi to control them by snacking. Additionally, various species of snails are native to different regions, some of which are more beneficial than others.
Caring for an Ecosystem Pond
While the goal of an ecosystem pond is to mimic nature, since your pond is manmade, its water will lack a natural source of movement. Therefore, you will need to create one. It is also important to regularly monitor your water quality, examining the pH, temperature, oxygen levels, and elements of the nitrogen cycle.
Circulation
The water in your pond requires a constant flow to remove debris effectively. The movement of the surface water helps skim off floating debris before it sinks to the bottom. Additionally, circulation maintains healthy oxygen levels in the water, which is essential for plants and fish. Proper circulation also ensures that stagnant water does not become a breeding ground for mosquitoes.
With a skimmer and waterfall feature, you can mimic a natural water flow. A skimmer is a piece of equipment that sits at the pond’s edge. It suctions water from the pond and traps debris, which you will later empty by hand. Rapid water flow is key. Setting the flow close to the maximum rate recommended by the manufacturer will often get the best results. Ideally, you want the volume of your pond to circulate through your filter every hour or two.
A waterfall is more than a decorative option. It generates movement, agitates the water molecules, and helps to “turn over” the water in the pond. Because water at the bottom of the pond receives less oxygen, it is important to install your waterfall on the opposite side of the pond from your skimmer.
Water Quality
In a healthy ecosystem pond, the water needs a stable pH, minimal-to-no nitrites or ammonia, and moderate nitrates. The pH scale measures free hydrogen levels in water, ranging from 1 to 14. Koi do best at levels between 7.0 and 7.6, where the water is neither acidic nor alkaline. It is important to hold pH levels as constant as possible. Rapid changes in pH can stress the fish and, in some cases, be fatal.
Ammonia is produced when fish waste, organic matter, and uneaten food break down. Even a small amount (above 1 ppm with an ideal pH balance) is highly toxic to fish. Nitrite levels also should stay below 1 ppm. Nitrate–the final product in reducing ammonia–should fall between 20 ppm and 60 ppm. Nitrate will become toxic to fish at 120 ppm.
If any of your water levels are off, it is important to perform a water change and add biological boosters. Additionally, you can add one tablespoon of saltwater per gallon (make sure to use non-iodized salt, not table salt). Clean the filter and increase aeration to enhance oxygen saturation.
Water Changes
Regular water changes are crucial to maintaining a healthy pond. They remove harmful chemicals and excess nutrients that can become toxic to fish or deprive them of essential oxygen. Additionally, water changes eliminate pheromones that can hinder growth and increase stress levels in fish while also reintroducing some depleted trace minerals.
Changing the water in your pond can be one of the riskier maintenance tasks for your fish. Koi and goldfish thrive on stability, which means they need consistent chemical balances, oxygen levels, and water temperature. Any time you introduce new water, it can disrupt this balance. Always test new water to ensure that its parameters closely match the old water. We recommend removing and replacing between 10% and 20% of the water every week or two.
Ecosystem ponds are a beautiful and rewarding addition to any backyard. They provide a habitat for a variety of plants and animals, and they can be a great source of relaxation and enjoyment. However, it is important to remember that ecosystem ponds require regular care and maintenance in order to thrive.
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