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Building a Native Pond

A native wildlife pond can be as simple as a shallow rainwater catchment for rainy season toads or a full-blown lake with a flowing waterfall and stream. Due to the problems mentioned earlier about keeping unwanted invasive species out, we encourage people to think long and hard about building a new pond. Your pond might some day, perhaps under the control of a new owner, become a nuisance pond harboring invasive species that could harm local wildlife. 

Perhaps a good compromise would be to keep your pond simple and small to make it easier to maintain and easier to disassemble in the event you decide to sell your house.

We’ve purposefully avoided going into details about materials and construction methods. There are many new products every year available locally and on the Internet and many different construction techniques. Do It Yourself books are readily available or hire a contractor. Instead we will supply you with basic guidelines for the design and habitat based structure of the pond.

Rainy Season Toad Pond

The simplest design is a shallow depression to facilitate toad breeding and to supply drinking water for wildlife. Our desert toads are not true frogs; they don’t need permanent water to survive. They spend dry seasons under ground and when summer rains come, they have explosive breeding events at favored water holes where their eggs will hopefully have enough time to hatch and turn into baby toads before the pool dries. Spadefoot toads are the quickest to transform from egg to toad and need at least 7 days of water, other species need up to 8 weeks. If you live on the outskirts of town or near an urban wash, you will likely have a toad population nearby. Listen for the calling males on rainy nights. If you identify your neighborhood toads to be of the more quiet variety like the spadefoot’s or the Sonoran Desert toad, you might consider building a toad pond.

Due to noise considerations, locate the toad pond well away from the sleeping areas of your home and your neighbors. A toad pond should be in a sunny location, about 2 to 3 feet deep and at least 5 feet in diameter with gently sloping sides to avoid trapping toads or other small animals that might end up in the water. Add 4 or 5 inches of rocks, gravel, sand and dirt to the bottom of the pond. If javelina or dogs will be visiting the pond, add extra rock to the shallows to protect the liner and make it less attractive as a mud wallow.

The pond should be still, without moving water. It should be temporary and let to dry during the winter months. This will avoid a buildup of aquatic predatory waterbugs that will feast on the toad tadpoles. A liner or concrete surface will help hold the water; you will need to keep water in the pond for most of the months of July and August to allow the tadpoles time to transform into baby toads. Plant a few clumps of deergrass (Muhlenbergia rigens) around the perimeter of the pond to add some cover. If you want to avoid irrigating any plants, use stick piles and rock piles around the edges and in the shallows so tadpoles have protection from predators. 

With the first strong summer rains, fill the pond, if it didn’t fill on its own. Add Bti mosquitoecide to the pond to keep mosquitoes from breeding. Be patient, it might take a couple years for the toads to find your pond but in the mean time it will surely become a great bird watching sight.

The Simple Frog Pond

The next simplest pond would be a permanent pond without moving water. Always locate ponds in open areas away from over hanging tree branches. This will help in maintenance when the trees drop leaves or bean pods that can dangerously alter the water quality of the pond. Make the pond deep enough to allow for a 6 inch layer of sand and dirt substrate in the bottom. This will give the plants something to root into and will allow for beneficial bacteria and microbes to help maintain water quality.

Without circulation, water quality and filtration is left to the plants and microbes. Your pond will need to be heavily planted with good oxygenating and filtering plants like Stonewort (Chara spp.) and coon’s tail (Ceratophyllum demersum). Avoid disturbing the bottom substrate as noxious gasses and chemicals that are a natural part of decomposition will be released into the water and could be harmful to fish. Goldfish and koi are not recommended for this kind of pond, when they grow large they will constantly stir up the bottom muck and uproot plants.

The Recirculating Pond

A recirculating pond is equipped with a pump that moves the water continuously. The moving water should be directed through some sort of a biological filter medium. The concept is simple; in nature a stream flows through rocks and gravel. The surface of the rocks and gravel is the medium for algae and microbes that can only grow in oxygen rich moving water. These plants and microbes feed on the nutrients in the water removing the harmful components. The plants in the pond are much more efficient at filtering the water when it’s moving as well.

A good design for a recirculating pond is to pump the water from the pond into the head of a stream. This is often done incorporating a waterfall of some type. The water then moves down a small stream flowing into the pond to complete the cycle.

The pond should have deep places with some large rocks for the fish and frogs to escape predators and some sunny shallows for them to warm up during cold seasons. Position the water intake, where the water leaves the pond and enters the pump, along a steep shaded bank where the baby fish and tadpoles will spend less time and be less likely to be sucked into the pump. 

If stream fish, like longfin dace (Agosia chrysogaster), are to live in the pond, supply them with clean wash sand in the stream pools and where the stream flows into the pond. They will use these areas to lay their eggs. Each year it will be necessary to replace some of this sand with clean sand to encourage more breeding.

Converting an Existing Pond to a Native Pond

Perhaps you already have a pond that contains non-native species such as goldfish, bullfrogs, and non-native plants - but you want to “go native” and convert your pond to native species. Even if you can’t get permits for native wildlife, there are ways you can make your pond more ecologically friendly.

Removing Invasive Species

The first step in converting a pond to native species is to eliminate the non-natives. The most drastic but effective measure is to consider drying the pond. May and June are our driest months and the best time to dry a pond. If any of the species in your pond are mobile, like bullfrogs, turtles and crayfish, you will need to set up a perimeter fence to contain them and make arrangements for possible removal. Contact the Arizona Game and Fish Department, Invasive Species Coordinator at (623) 236-7600 or the University of Arizona, Department of Ecology and Evolutionary Biology (520) 621-3187. As the plants are drying, remove them and haul them off to the county landfill.

Removing Nonnative Turtles

Turtles like red-eared sliders and painted turtles are commonly found in urban parts of the Southwest and are frequently finding their way to our wetlands. Turtles can be easily attracted to traps with bait such as canned tuna. Turtle traps can be purchased online. If the pond is small, try lowering the water level and then you should be able to net the turtle with a dip net.

Removing Crayfish

Crayfish removal requires a thorough drying of the pond and surrounding soil. Dry the pond in early May and keep dry until the rains come in July. All plants in the pond should be removed. Crayfish will burrow into the soil around the perimeter of the pond so any holes should be searched out and dug-up. Keep watch on the pond as the water is being removed. Gather any crayfish that try to leave the pond. Crayfish can be easily killed by freezing overnight. 

Removing Clams and Snails

Aquatic snails can be beneficial to the native pond by consuming algae. Snails will hitchhike on the plants you acquire and are almost unavoidable. There are invasive species of snail like the New Zealand mud snail that are very difficult to tell apart from native snails and very little information exists on other common snail species. Introduced fresh water clams are of major concern over their impacts on wildlife so it’s best to avoid all clams. Drying the pond is the only practical way to remove either mollusk.

Removing Bullfrogs

If the pond is not too large, bullfrogs can easily be removed, but their tadpoles present a challenge. The frogs will attract to a spotlight if the light is left on for several consecutive nights. Set up the light at the edge of the pond, aimed at the water, along an open shoreline where you can easily approach from behind the light. The blinding light will hinder the frogs ability to see you and you should be able to get close enough to net them. Some will get away and become wise to your technique so leave the light on for a few nights before you try again. Some pond owners in rural areas prefer to use a BB gun for bullfrog removal. BB’s are nontoxic and unlikely to puncture a pond liner, however, shooting is not a legal method of take for bullfrogs. If a captured bullfrog needs to be destroyed, the most humane way is to bag it and throw it into your freezer overnight.

Search the edges of the pond and plants for egg masses (pictured in side column). When removing egg masses be aware that very small tadpoles might be emerging from some of the eggs. These helpless black “slugs” lie on the bottom of the pond under the eggs, unable to swim for the first few hours. These very small tadpoles can be easily gathered in a fine mesh aquarium net. The eggs will be quickly destroyed if allowed to dry in the sun. Any tadpoles that might emerge from the eggs as they dry will not be able to get to the water and will quickly succumb.

Free-swimming tadpoles in the pond are much more difficult to catch. Funnel shaped minnow traps can be purchased at sporting goods stores. These traps can be quite effective at catching tadpoles and fish without the use of any bait. Without drying the pond, it will be close to impossible to get all the tadpoles. Try lowering the water level to help in the removal effort. You can also try waiting a year or two for the tadpoles to transform into young frogs and then revisit the spot light strategy.

Removing Fish

Fish are even more difficult than tadpoles to remove as they are much quicker and the tiny babies and eggs are almost undetectable to the human eye. However, in relatively small ponds, persistent efforts to net and trap out fish have proved successful. Employ the minnow traps mentioned in the tadpole section, retrofit the traps with window screen if the mesh is too large to contain the target fish species. Try baiting the traps with a few pieces of dry dog food. Along with the trapping, you will need to spend a lot of time stalking fish with a net around the edges of the pond. Lower the water level to isolate the fish from dense vegetation. Try using a headlamp or flashlight at night to see and net the fish. Just when you think you’ve gotten the last one, there will probably be very small babies hiding out so wait a couple weeks and do it again. Fish can be humanly dispatched by freezing or donated to a zoo or university.

This toad pond is a bowl shaped depression in the lowest part of a large rainwater collection basin. The liner will hold water long enough for tadpoles to transform into tiny toads. Supplemental water can be added if necessary.

Some desert toads like the Great Plains toad (Bufo cognatus) are quite loud and could keep your family or your neighbors up at night.

A simple frog pond relies on plants to maintain water quality. A float valve can be incorporated to maintain the water level.

Recirculating pond with stream habitat is ideal for native fish like longfin dace. Notice the abundance of deer grass providing shade and cover for the fish and frogs.

For native frogs, stack slabs of concrete or flagstone with 1 to 2 inch spacers along the shoreline that gets the most sun exposure. Angle the slabs slightly so the crevasses between the slabs have air pockets where the frogs can hide for extended periods of time. These pockets will protect sluggish frogs on cold winter nights when they are extra vulnerable.

The red eared pond slider is a turtle species that is threatening native species worldwide.

Crayfish sometimes called crawdad or fresh water lobster are extremely harmful to wilderness wetlands.

Malaysian trumpet snails are common in backyard ponds and aquariums. Their effects on local wetlands are not well understood.

The bullfrog, native to eastern U.S., eats anything it can get into its large mouth. Recent studies have implicated these frogs in spreading a deadly disease to native leopard frogs. Bullfrog tadpole shown in lower photo above.

Bullfrog egg masses can be anywhere from 4 inches in diameter to the size of a diner plate. One egg mass can contain as many as 20,000 eggs.

The tiny mosquitofish has been introduced worldwide displacing native species. This picture shows a group attacking a native leopard frog tadpole. Avoid this fish!