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In Part 1 of this three-part series, the philosophy and mindset for building ponds for wildlife was covered. Revisit that article here. This article, Part 2 in the series, describes how to go about designing your pond.

Choose the Site, the Size and Design the Perimeter

Contrary to what you might think, a wildlife pond is best built NEAR your home. By placing the pond within sight, you’ll not only get more enjoyment from it, but you will also be aware immediately of anything that needs attention. The pond above is just outside the kitchen window and deck.

One couple built their wildlife pond at the back of their lot, with the idea of going to it as a meditative place. When they failed to meditate for several consecutive days, an awful sight greeted them: the raccoons had rearranged their waterfall, and all the water had flowed out of the pond. It was dry, and those critters that couldn’t live without water to support them were dead. They lost all their polliwogs, dragonfly and damselfly nymph, countless larvae of underwater beetles, and others.  

When your pond is near your house you can also use your windows as “observation” posts and photography blinds. Having a pond outside a kitchen window greatly increases the joy of dish washing! A camera with a zoom lens is helpful for securing good images of your wildlife visitors and don’t forget to keep binoculars handy.

Though most lilies and other pond plants found in nurseries prefer sunny locations, you can site your pond under a tree! On the other hand, if you place your pond where leaves can fall into it, your workload will be increased. If your pond is under a tree, stretch bird netting above the pond in the fall to catch leaves (as in the photo to the left). If the netting is placed at a sloping angle, it can be shaken and the leaves will tumble down, perhaps into a strategically placed wheelbarrow.

Whatever size you are considering, you probably should increase it. Build your pond as large as you can, as a larger pond is more stable. It is best if you can reach into all areas of the pond for maintenance, but that should be your only limiting factor. The British Dragonfly Society did a study to determine the best size for a pond designed for dragonflies. Their recommendation: build a pond that is 15 x 20 feet (4.6 x 6.1 m). With a pond that size you can reach from the edges to the center for debris removal and the temperature of the water will remain fairly stable due to its volume.

You’ll want to provide both shallow and deep areas, including a level planting shelf approximately 18 inches (45.7 cm) deep for potted aquatic plants. A depth of three feet (91 cm) will provide an area where the water temperature is more constant, and where small creatures can hide from larger predators such as herons and kingfishers.

Liner ponds will work best as they can be more naturally shaped. Forty-five mm EPDM liner material is a good choice. Concrete ponds might crack and split with age and need treatment to prevent toxic chemicals from leaching into the water. Pre-formed polyethylene molded ponds do not come with shallow edges or in large enough sizes for a wildlife pond. Another option, especially when building a large pond, is an earth-bottomed pond. This design requires large equipment, however, so this type is not well suited for a backyard pond.

Wildlife ponds should have a beach. This will provide not only a way for wildlife to enter and exit your pond, but also a way for YOU to get in and out. Your beach should be built with “steps” leading into the deepest part of the pond. You will need to enter your pond to do maintenance, a delightful experience on a hot day. In fact, such days are the perfect time to do upkeep! Construct steps by filling gunnysacks with soil from your yard and place them between the liner and the pond bottom. 

A path around the pond, as seen in these photos, allows you to get close to the water. It also makes it easier to reach into the pond to do maintenance. One artistic “trick” is to make your path narrower as it moves away from your beach. This creates the optical illusion that the pond is larger than it really is.

Varying the edge treatments will not only make your pond look more natural, but wildlife will be able to choose their entrance and exit spots with an eye towards concealment and other safety considerations. Please avoid the “necklace” effect of using paver rocks as edging as much as possible. It will not look natural and your smaller creatures will be vulnerable and exposed as they cross it. Substitute more varied and natural materials than just rocks and stones. A log can be used as a part of your edge treatment. It also makes a nice “bench” for friends to dabble their toes from on hot days!

One source for logs is the cull piles in our national forests where timber companies have logged. Logs in these piles are destined for burning, and, by using one, you help avoid contributing to air pollution! The log we used, next to the path in the photo above, is actually partially hollowed out and was placed over cement bricks. The pond liner goes up and over the cement bricks under the log. This log has become a favorite spot; it mimics places I’ve found and enjoyed in nature.

You probably will want to use some rock edging. Check out what is available locally. Stones and boulders that naturally occur in your area will look best. If rock collecting is legal in your area, searching for your own stone can be a rewarding experience. Otherwise, buy your rocks from local landscaping and rock yard shops. Distribute rocks elsewhere in your yard to tie the pond to your land and make it look as if it were always there.

Rocks can be secured in place with expanding spray foam insulation. Make certain that you choose a nontoxic brand that will be inert once it dries. Handfuls of your local dirt can be thrown on the foam as it is drying. It will adhere and make the area look natural, thereby disguising the foam’s appearance. Spray foam must be used on a dry, not wet, surface. Therefore it may be necessary to drain the pond down a foot (.3 m) or more after testing that the edges are indeed level.

Even when using a pond liner, it can be difficult to create variations in the edging contours without forming “wrinkles”. Yet these contour changes make the pond appear more interesting and natural. They also create microclimates.  

If you have areas of lawn in your yard, allow one section of the lawn to abut the pond edges to help tie the two areas together. But a pond ringed only by lawn will look out of place and lonely.

One or more bog areas next to your pond will provide ideal entry and exit points for many creatures. The foliage provides cover, shade and dampness while serving to tie the pond in with the rest of your yard.

Bogs can be placed in both sunny and shady areas. The sunny bog in the picture above is situated between the path and an edging boulder. Yellow seep monkey flowers (Mimulus guttatus) are blooming in this May photograph.

When deciding on the placement of your pond, it’s wise to consider the natural runoff on your land. It is a mistake to put your pond in the lowest area of the yard. This is NOT a good idea because the water that flows through your yard may have originated across the street, or farther away. It may contain pollutants such as herbicides, pesticides and/or oil that would be very harmful if they entered your pond.

Build berms around your pond so that runoff cannot enter. Waterfalls, bogs and logs are all good ways to create berms that appear natural.

Another way to provide overflow drainage is to create a creek bed, lined with pond liner material and covered with rocks. In the photo above, a deer drinks from the pond at the overflow creek-bed site. 

To some extent, bog areas next to the pond will also allow some drainage.

A wildlife pond does not have to have recirculating water, but there are many benefits to using a pump. Stagnant water is more likely to develop algae and host mosquitoes. Aquatic creatures need oxygen and recirculating water has more of it. This is true partly because the waterfall creates ripples on the water and oxygen diffusion occurs there. Think of it this way: the surface of still water is flat, so a string going across the pond would measure the surface diameter. But a waterfall creates ripples, so a string going across the pond would have to go up and down with each little ripple. Thereby the measurement of the diameter is increased allowing for greater oxygen absorption.

A waterfall makes a wonderful addition to any pond, and it can serve as one of your edge treatments. Waterfalls, besides being aesthetically pleasing, also discourage mosquitoes, which prefer still water. The pleasing sound of a waterfall helps mask other noises in your neighborhood, and many people find the sound of falling water restful, helping to ease the tensions from a stressful day. Birds are attracted to the sound of moving water that a waterfall produces and will often choose this site for their drinking and bathing.

One way to construct a waterfall is to pile the soil you excavate to the far side of the pond. Use pond liner and rocks to create a stream-like waterfall (photo above left). Or, if the slope of your yard is downhill, then you can bring in large boulders and have them artistically piled on top of each other (photo above right). This waterfall was built with four boulders. Two of the boulders create the base of the waterfall and a cup-shaped boulder serves as the top. The fourth boulder was placed to the left of the waterfall, to give continuity to the design. The recirculating pump was positioned in the deep area, as far as possible from the waterfall itself. Flexible piping (dark colored is best) runs from the pump to between the two boulders at the base, and then comes up to the top of the cup-shaped boulder from behind. A splitter at the end of the tubing is concealed under a few flat rocks and the frog sprinkler.

Soil was added behind the boulders and a “skirt” of soil, held in place by black plastic within a mesh of wire (bird netting also works), surrounds the cup-shaped boulder and is planted with polypodiums and five-finger ferns (Adiantum aleuticum).

Having water falling from an overhang increases the sound effect and is pleasing to the eye. It apparently is pleasing to frogs too, as our native frogs have found that it naturally amplifies their “chorus”! 

Your waterfall rocks and recirculating pump will be your main expenses, other than the pond liner itself. Research these expenses on-line. Be certain to choose a magnetic pump, rather than one that uses oil: a pump that uses oil can create problems. If roots get into the pump and it burns out, the oil will be released into the pond. Luckily, oil floats. If such a disaster should occur, contain the oil spill with a hose and then overflow your pond by adding water at the opposite end from where you want it to overflow. At the overflow site, place newspapers. The oil will float off and be absorbed by the newspapers while the water flows through.

It can be beneficial, especially with a larger-sized pond, to add one or more smaller water features such as a “frog spitter” or some other type of ornamental water display in a different area (photo at right).

Design the Interior of the Pond

One of the main ways a wildlife pond differs from a koi or tropical lily pond is the edge treatment. A wildlife pond should have shallow edges. Unlike tropical ponds where the sides are purposely built with a steep edge to prevent raccoons and other creatures from entering, a wildlife pond embraces and encourages entry by wildlife and humans as well.

Your wildlife needs the gently sloping sides to get in and out. We once visited an owner whose pond for wildlife was on their mountain property. But it was built with steep edges. One day when they returned from a trip, they found a dead fawn in the pond. It had stepped in and had been unable to get out!

The area beyond the planting shelf in the diagram is shown in dark green; this deep area is needed to give stability to the pond’s water temperature. It also provides a place for creatures to hide from predators, and a place for them to overwinter, when deep water will be the warmest. Remember that steps into the pond for your own use increase safety. Gently sloping pond liner material, especially with a layer of natural pond slime on it, can be very slippery!

It is wise to provide an escape route. A log or some branches that transcend the pond edges (extending from inside the pond to several inches or even several feet outside the pond) offer any small creatures that fall in an escape route. An object that bisects the edging also is an artistic trick that “anchors” the pond to the surrounding terrain. 

Build Your Pond Slowly and Don’t Be Afraid to Let It Evolve

There is no reason to rush the development of your pond. Take your time and enjoy the stages. You’ll find that some plants may “migrate” to where their individual needs are better met. If you let this occur naturally, your plants will be healthier as they “know” where they will grow best!

Control Algae

To control algae: cover two-thirds of the pond’s surface with floating and/or emergent plants. These plants will not only provide shade, which lowers your water temperature (warm water encourages algae), but they will also use some of the nutrients in the water, thus starving the algae which would otherwise flourish on these same nutrients.

In the photo above, the Elodea (underwater plant) was allowed to grow to the surface where it formed a mat and bloomed with tiny white flowers. If the mat is unsightly or accumulates debris, it can be trimmed back periodically with hedge trimmers: the perfect task for a hot day! 

Another method to control algae by starving it is to use a filter, preferably a biological filter.

Be aware that although algae may be unsightly, it is a natural occurrence. Every pond will have an algae bloom its first year as the plants have not yet had time to grow large enough to provide the balance needed to starve the algae. Don’t despair or quickly rush to use chemicals in your pond. Be patient. The second year the spring algae bloom will be much less intense, the third year even less. 

Pond Filters

A recirculating pump will benefit most ponds, but you can build a pond without one, using only the plants in the pond to filter the water and using a net to remove debris. Dragonfly Roost pond, to the left, is an off-the-grid, totally unfiltered pond. It does have low inflow and outflow though, with the inflow arriving in the bog area where the plants provide some filtration (bog area in photo is to the back right). 

A mechanical filter simply removes suspended solids in the pond water. A biological filter, which is more complex, can operate much like the “under gravel” filters in fish tanks. The biological filter can be designed as part of the pond itself or be housed in a separate tank. Read about filters here.

Control Mosquitoes in a Wildlife Pond

Although moving water, such as a waterfall, helps discourage mosquitoes, sometimes a more direct approach is necessary. Besides being “pesky”, mosquitoes can carry disease, so although they are a part of our natural environment they are NOT something you want to have breeding in your back yard (or front yard either!).

In many areas, mosquito abatement agencies distribute free “mosquito fish” (Gambusia affinis) to pond owners to help keep the number of mosquitoes down. However, these fish are not native to all regions in the USA; they occur naturally only in the Gulf of Mexico watershed. In the western USA, in particular, our native Pacific tree frogs (Pseudacris regilla) have evolved in ephemeral ponds and their polliwogs have not developed the habit of evading fish as predators. Ephemeral waters do not persist year-round, evaporating as the season progresses, and are, therefore, fishless. Frogs worldwide are in trouble; they are not breeding successfully and they are dying out. We need our ponds to be a refuge for them, not a death trap.

You can learn more about mosquito fish and to which areas they are native at this Wikipedia link.

What works well in all backyard ponds for mosquito control is a natural product that harms ONLY members of the Diptera family. The Diptera family includes mosquitoes, black flies, and crane flies. By floating “donuts” impregnated with the bacillus Bti (Bacillus thuringiensis israelensis) in your pond, you kill the larval stage of all members of this family, but NOT the members of other insect families, nor any mammals, amphibians, reptiles, or fish.

Use of Bti will reduce the total amount of critters in your pond. However, it will also reduce the amount of “food” for some of the residents, such as dragonfly and beetle nymph. Dosage charts on the packaging describe how much to use and how often to replenish the dunks. In a pond the size of Bigsnest Wildlife Pond, one dunk weekly keeps the level of Bti constant. We recommend using a Bti product as your first line of defense against mosquitoes. It is available at most nurseries and at hardware stores.

Should the Bti not work, or if they are not economically feasible, we recommend you use a NATIVE FISH species. You will need to research what fish are native in your area. In many areas of the world stickleback fish are native. They are about the same size as mosquito fish but are surface feeders, while mosquito fish feed at all levels. This means that sticklebacks are much less likely to feed on the polliwogs and dragonfly nymph, though they still may to a small extent.

Now you’re ready to build your wildlife pond! Next issue’s Part 3 of this series will cover how to maintain your pond.