Building a Backyard Fish Pond with Waterfall

Deciding on Type of Pond

Koi pool – a koi pool requires special consideration. It is generally called a pool because it does not contain many plants, if any. Koi are vegetarians, and will make it very difficult to keep aquatic plants in the pond. If you wish to keep koi, plan on having a large pool with a very good filtration system. You should filter at least 100% of your total pond volume every hour to ensure proper water quality and a healthy pond. I strongly recommend a UV light, such as the Tetra Pond Greenfree Clarifier, to keep the water free of suspended algae, since plants will not be able to help shade the pond or remove the algae-causing nutrients.

Mixed pond – a mixed pond is just that. It is a mixture of various types of plants and animals. You may have fish, amphibians, snails, bog plants, oxygenatingplants, lilies, and marginals. Filtration is still important, but is usually at a reduced flow rate of 50% per hour through the filter. Once the pond is established and balanced, suspended algae may not be a problem, and a UV light may not be necessary. To help reach this balance, I recommend the Tetra Pond ClearChoice Biofilter along with Tetra Pond Aquazyme. Please be patient and stock your fish and other animals slowly. It may take up to two months or longer to reach a balance with your pond.

Water garden – a water garden is a pool containing various plants. It will have oxygenating plants in the deeper areas, marginals and bog plants along the outer edges, and possibly some lilies. In this type of pond, the plants are the main focus. Filtration is not necessary as the plants do the filtering themselves. However, keep in mind that water that stands still can become stagnant and may breed mosquitoes. For healthy plants and beautiful blooms, fertilize monthly with Tetra Pond Florafin for all plants, or Tetra Pond Lily Gro for lilies and potted plants. During particularly warm summers, you may wish to fertilize every two weeks. To make planting aquatic plants easier, use Tetra Pond’s AquaPlanters.

Fish and Plants

Most people think of goldfish and koi when they think of pond fish. However, there are many other types of fish which make suitable pond inhabitants as well.

Common Goldfish – grow up to 12″, very hardy, good in all types of ponds. Plan 30 gallons per adult goldfish.
Koi – grow up to 30″, hardy, best kept in small quantities in larger ponds. Plan 100 gallons per adult koi.
Shubunkins – short finned fish which looks similar to goldfish, but with mottled coloration.
Exotic goldfish – best suited in summer ponds. Not as hardy, needs to be brought in for the winter. This group would include lionheads, orandas, blackmoors, bubble-eyes, etc.
Golden Orfe – a relatively fast swimming, hardy type of pond fish. May be sensitive to medications and other chemicals. Schooling fish that prefers to be near the surface of the pond, therefore making itself very visible to the pondkeeper . Grows up to 24″.

There are many other types of fish, such as minnows, sturgeons, guppies, tench, rudd, even tropical fish such as swordtails, mollies and plecostomus, which may be kept in ponds, but for the basis of this article, I have chosen the most popular and common varieties of fish.

There are other animals you may wish to keep in your pond. Snails, tadpoles/frogs, turtles, and crayfish are just a few. These animals may be more sensitive to medications and chemicals. Also, frogs and turtles may come and go. They do not necessarily make themselves permanent residents, but are certainly fun to have around.

The main plant associated with ponds is the lily. For overall loveliness, the lily can only be bested perhaps by the lotus. Here are some of the more common plants kept in mixed ponds or water gardens.

Lilies – these lovely blooming surface plants can be divided into hardy or tropical. They can be sub-divided from there into day or night blooming. Most lilies need to be planted around 18″ deep into the water. They prefer still water and require at least 6 to 8 hours of sunlight per day.
Water hyacinth – this plant is considered a weed in many states, it is so prolific. It requires little other than to be placed on the surface of the pond, where it floats. This plant makes a great nutrient filter for the pond. As this plant is mostly tropical, it needs to be over-wintered indoors.
Elodea – this is considered a pondweed, and can become invasive. Thin regularly. It requires deep water in full sun and makes a terrific oxygenator. It can overwinter in the pond in most areas. Usual recommendation is one ‘bunch” or five or six stalks of the plant, per square foot.
Pickerel Weed – this is a hardy, deep water marginal preferring to be planted in moist soil down to 10″. Enjoys full sun, and grows to 30″. This plant can over winter in the pond if planted near the 10″. In shallower waters, protection from the winter temperatures must be given.
Yellow flag – another deep water marginal. Plant down to 12″. This is a hardy plant with lovely blooms. There are many cultivars of this plant. Wild varieties grow up to 4 feet, while the cultivars range from 24″ to 36″. All types like full sun.
Arrowhead – a shallow water marginal, prefers to be planted down to 6″, in full sun. Most types grow to 24″
Water irises – one of the most popular and beautiful of pond plants. Prefers moist soil down to 4″ in full sun. Will grow to 30″ or better. This plant is of ten chosen to be a good nutrient filtering plant in fish ponds.

There are many other wonderful plants for ponds, but these are some of our favorites because they are readily available, hardy, and lovely.

Water Features

To design a stream or waterfall, start with your initial pond design. Ponds can be adapted relatively easily, by a variety of methods, to form a waterfall or stream. Running water features can be either ready-made forms or home built. Ready made waterfalls, etc, are generally easier to install, but may not look as natural.

Water features can be a fountain, waterfall, cascade, header pool, stream, or a combination of the above. Make sure you use a liner under any of these, regardless of whatever else you may be using to make it, as a backup for leakage. For instance, you may wish to mortar flat stones together for your waterfall, but placing a liner underneath these stones will help prevent water from escaping around the rocks.

For most streams, plan a gradient between 10 and 30 degrees. Streams should be relatively straight and uncomplicated. If you intend to have several small shallow pools in the stream, the gradient should be very gentle. Plan the width of the stream so that it will appear full when the pump is running.

Waterfalls should be constructed to appear as if they are a natural part of the landscape. Therefore, they work best in ponds on gently sloping ground. However, you can use the dirt from the excavation of your pond to build a waterfall behind it. Just pack the dirt down as tight as possible, then carve out the steps for the waterfall. You may need a retaining wall made out of stones. Again, be sure to use a liner over the steps of the waterfall before mortaring or poly foaming in any stones. The liner should generously overlap the lower liner leading into the pond. Be aware of capillary water losses due to fabric underlay meeting with the water level or from folds in the liner. The height of your waterfall should be in proportion to the overall pond.

Use large, flat rocks for the waterfall spillway. They should have a nice, crisp, clean edge, and be tilted forward, to get the most flow. If they are not tilted forward, water may be encouraged out the back or sides of the waterfall. Large, heavy stones need additional support in the form of concrete pads or crushed stone. If the stone weighs more than 100 lbs., use at least a four inch thick concrete pad beneath them. Heavier stones may require rebar for reinforcement. You may wish to mortar the main waterfall stones in place or another choice is to use quick drying poly foam, which can be purchased at most building supply stores. Keep some sand handy, and as you spray the poly foam in a particular area, quickly toss some sand on it to help camouflage its color. Also, wear gloves and have a stick available to push the poly foam back into the crevices.

Once your main waterfall stones are in place, make sure you draw the liner up the sides. Keep checking to make sure it is above the water level. Begin to fill in the sides with other stones. Place these stones carefully as they can be used to direct the flow of water. For instance, a stone placed directly in the flow of water can change the direction of the flow and even increase it. The top of the waterfall should be such that it hides the hose. To control the outflow from the hose, attach a bar-tube to the end of it. Prior to doing this, bore several holes along the length of the bar-tube and plug the end of it. This will ensure that the water comes out less vigorously. Run your waterfall frequently during installation to check for any problems , and to see if it gives the appearance you wanted. If you wish, you can carry a garden hose with you, and run water down the waterfall as necessary, without the use of a pump. Any areas that appear to be allowing water to bypass the actual falls should be filled in as necessary with stones and poly foam.

I am sure you have noticed I continuously recommended poly foam. Mortar can be used but there are a couple of disadvantages to mortar. It must be sealed to prevent the leaching of lime into the water which can drastically affect your pH. Also, in areas where cold weather occurs, you will find yourself making yearly repairs to cracking or separating mortar.

Header pools are usually used as a reservoir from which water will spill over a waterfall, cascade, or stream. They are usually constructed at the top of the water feature, and hidden by sinking them into the ground and surrounding them with plants. For a more natural look, fill the pool container in with pebbles. This makes it look as if the water is actually coming from an in ground spring.

Cascades are similar to waterfalls, although the water travels from a header pool, down a series of steps to the main pool. These pools are carved out of the ground as you proceed down a gentle slope, and are very shallow.

To figure your flow rate prior to actually installing a stream or waterfall, allow at least 50 to 60 gallons per hour per inch of lip (the lip is the actual edge the water flows over). For instance, if your waterfall is 18″ wide, you want a pump with a minimum flow rate of 900 gph. Be sure to look for the “head of water” outflow rate on the pump, prior to purchasing it. This will tell you how much water it pumps per foot in height of the waterfall or stream. For example, a pump may be rated 1,000 gph. But at 4 feet of height, it may only pump 725 gph. This number is the important one when considering the flow of your waterfall or stream. Pumps vary. Keep in mind that they may actually pump +/- 20% what they actually state on the package.

Fountains

Fountains take little consideration. They do not require major plumbing, and offer a lot to the pond. They sound beautiful and look lovely, as well as aerate the pond. There are many different sizes and types of fountain heads, so you are bound to be able to pick one that suits your tastes and your needs. Some pumps are large enough to operate both a fountain and a waterfall, so you may want to plan this in advance, or purchase a smaller pump, just for the fountain. The Tetra Pond Fountain Set has five different fountain sprays and is recommended with the Tetra Pond Typhoon Category 3 pump.

Filtration

As stated earlier, if you are planning on building a koi pool, you should filter your water 100% every hour. For our purpose here, a mixed pond with plants and various fish, snails, etc, I recommend 50% of your total water volume, to be filtered per hour.

Filtration comes in many forms. Larger ponds often require PVC piping under the pond to an external, in ground filtering system. Such filtering systems are not always in ground, but this is quite common because it is very difficult to hide such systems with landscaping. In such a large pond, you may wish to install a bottom drain while installing your pond. Bottom drains may be opened, to allow for cleaning or draining of the pond. An external pump is attached, through PVC piping, to pull water through the drain and to an overflow area. This makes cleaning much easier. Make a hole in your liner that is about half the diameter of the pipe. Force the liner carefully over the inlet of the drain. This creates a pressure seal so that no glue or adhesive is needed.

For most smaller ponds a bottom drain may not be necessary. It is a simple matter to use a garden hose as a siphon to clean or drain the pond, or even use a shop vac for such a purpose. So for ponds up to 2,400 gallons, filtration can be a relatively simple matter. The ClearChoice PF1 is an external filter for up to 1,000 gallon ponds. Recommended flow rate should be between 300 and 500gph. The ClearChoice PF2 is also an external filter and is recommended for ponds up to 1,800 gallons. Recommended flow rate is between 500 and 750gph. The ClearChoice PF3 is our largest external filter, for up to 2,400 gallon ponds. It will take a flow rate of 1,000gph.

Tetra manufactures one submersible filter called the ClearChoice Submersible Filter. It will keep ponds up to 1,000 gallons balanced and clear. Use as your only filtration system or as a prefilter to reduce the amount of clogging that occurs in your pump.

Plumbing is very simple for our external filters. The PF1 and PF2 come with three inlets, a 3/4 inch with venturi, a 1 inch with venturi, and a straight, universal inlet, with no venturi. The latter will accommodate tubing of 1/2 inch to 1 inch. The outlet on both of these filters is 11/4 inches. So you can choose most any size tubing or hose to connect the filters to your pump. The outlet, however, must be at least 11/4 inches. Any smaller, and it may restrict the flow of water and cause your filter to back up.

Tips to remember when installing a ClearChoice Biofilter:

Place the filter above the level of the water because it gravity feeds back into the pond. If it is below the level of the water, the flow will be restricted, and water may either back out the venturi on the inlet, or out through the lid.
Make sure your inlet is at least 3/4 inch and the outlet is 11/4 inches for proper flow rate.
Follow flow rate recommendations to avoid leakage from the lid.
Check your spray bar and pads for clogs periodically. Water may back out the venturi if a clog occurs and is left unattended.
Do not install your biofilter underground.
Break down your biofilter and store properly for the winter.

This article was meant as a starting point for would-be pond hobbyists. I hope you found it informative, and useful. For more detailed information and additional assistance, contact your local retailer or check out one of these references.