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Plan a pond


Whatever your lifestyle and garden, there’s a water feature to suit you. Water gardens can be natural or formal, vibrant or reflective, intimate or elaborate. If you’re considering a pond but haven’t taken the plunge, read through this practical planning guide to find out if you’re ready to have a water view at home.

Define your goals

First, decide what’s most important in a water garden. Do you want something beautiful to look at? Are you interested in caring for fish or unusual plants? Is hearing the relaxing sound of running water your main objective? Think carefully about why you want a water garden, write down these goals, and share them with your landscape designer or anyone else who’s helping with the process. Clarifying your goals will help you choose the right site, size, and design for your water feature.

Choose the site

Pick a location you’ll see often from the outside and inside. You might want the water feature near your kitchen window, for instance, or beside the patio where you have outdoor meals. The more you see your pond, the more you’re apt to maintain it, so keep it in sight where you can enjoy it year-round and fix problems quickly.

Water gardens look beautiful in many locations, but there are pros and cons to each spot. If you build a water feature on a slope, you’ll spend more time designing and building it, but you’ll end up with dramatic waterfalls and multi-leveled pools. Wooded ponds look natural and attract wildlife, but cleaning out fallen leaves and sticks will take up a lot of time. Sunny or semi-sunny spots are often best. Although you’ll have to keep algae under control, water plants thrive in these locations.

There are places where water gardens definitely don’t do well—especially boggy, low-lying areas where rainwater accumulates. It may seem natural to plan your water garden there, but rain runoff sometimes drags along fertilisers and debris from surrounding areas, creating a biological imbalance in your water feature. Build your pond close to a source of water and electricity to make the project easier and less expensive. Always check for water and electric lines before digging.

Ponds may pose a threat to a young child’s safety. If you have infants or toddlers in your family, postpone building a water garden until your kids are older or build a “pondless” water feature. These water features are either filled entirely with pebbles or are topped by a strong gate with pebbles on top, making them safer for children.

Plan big

It’s best to design a bigger water garden than you think you’ll want, especially if you want to add fish. Large, deep ponds hold more fish and plants, they’re easier to see from a distance, and they achieve an ecological balance better and faster than small ponds.

If you want fish in your water feature, plan a pond that’s 2 feet deep in at least half the area, with varying depths in other areas (no more than 5 feet at its deepest). Shallow water gives water plants a good place to grow, while deeper areas offer fish cool water and a place to hide from predators. Ponds without fish don’t need as much depth or variation.

Keep water clean

Every water gardener dreams of clear water, and you can have it—up to a point. Be aware, however, that your pond will never be crystal clear. Two kinds of bacteria, nitrosomona and nitrobacter, must be present to transform the toxic ammonia in the water (from fish excrement and decaying organic matter like fallen leaves) into healthy nitrates (which act like fertiliser for your plants). So don’t remove that slimy green film on the sides of your pond and rocks—it helps your water’s ecosystem stay healthy.

Algae, however, is something you need to monitor more closely. It can look like individual hair strands linked together or a thin, green mat covering the water. By the time a water garden is about three years old, algae problems often resolve themselves. In the meantime, and to help keep algae under control each year, include enough surface-floating and deep-water plants so that 50 percent to 70 percent of the water is covered by foliage and flowers in summer. (Algae won’t grow well in shade.) Also, put in submerged plants to starve algae of food. In addition, chemical and organic products are available from nurseries and pond stores to help limit algae growth.

All these strategies help control algae, but in spring you’ll always have more algae simply because water plants aren’t yet providing shade. Just practice patience, use a plastic garden rake to periodically remove the algae, and wait for algae to die back in summer.

Consider adding fish
The most common mistake for beginners is to put too many fish in their ponds too soon. By limiting the number of fish, you decrease the amount of toxic ammonia the fish excrete, which leads to higher water quality. Experts suggest adding only one goldfish per 25 to 50 gallons of water in a new pond. After a few months, once your pond is ecologically balanced with plenty of plants and healthy bacteria, you can increase the ratio to about one goldfish per 15 gallons of water.

Goldfish are relatively small, social fish that coexist well with other species and plants. They’re available in a wide range of colours, and some sport elegant fins and tails. Measuring 6 to 10 inches, they’re fairly hardy in both cold and warm climates. Goldfish live through the winter in zones 6 to 10 and go dormant at the bottom of a pond in water temperatures between 36°F and 50°F. Keep a hole in the ice all winter (via a waterfall or fountain) to provide oxygen to the fish and to release gasses from dying plants. In colder zones, you’ll have to bring your fish inside for the winter, which can require a large aquarium and high maintenance.

Unless you’re a dedicated koi enthusiast, stay away from these beautiful swimmers. Koi, an ornamental carp, grows up to 3 feet at maturity, requires much larger pools, and damages many water-garden plants.

Get the right equipment

The type of pond equipment you need depends on the size and purpose of your pond, and also the amount of maintenance you’re willing to do. Consult an experienced water-garden designer to discuss what works best based on your needs and budget.

If you want a simple pond with no fish, you probably won’t need any filters. If you add fish, however, you’ll need a mechanical filter that traps debris so you can manually clean it out. And you’ll need a biological filter, in which bacteria attaches itself to plants, rocks, and other surfaces in the filter and cleans water as the water moves through. Sizes and prices vary widely. You’ll also want to research various fountains and liners. In the end, you should have a pond that meets your goals with the least amount of maintenance.

Plants for the Pond

There are five types of plants that provide beauty and ecological balance for your water garden:

¦ Submerged plants remove nutrients from the water so algae can’t thrive. These plants don’t need soil. Just put them in one-gallon pots filled with pea gravel and place them in the bottom of your pond.

¦ Deep-water plants (or floating-leaf plants) such as water lilies (Nymphaea) grow in pots placed 12 to 36 inches deep and have foliage and flowers that bloom on top of the water’s surface. Along with surface-floating plants like butterfly fern (Salvinia rotundifolia) and fairy moss (Azolla filiculoides), they provide shade, which limits algae growth. Surface-floaters, which also help starve algae by depleting the water of some nutrients, require no planting. Just put them in the water and their tiny leaves reproduce rapidly. Most of these are considered annuals in colder climates.

¦ Shallow-water plants like the hardy canna (Thalia dealbata) grow in mud or 12 to 18 inches of water. Arrange them on platform shelves on the edge of your pond to conceal the water garden’s artificial edges. Keep these plants in fabric or plastic pots, then place the pot under water and let the leaves grow in the open air.

¦ Bog plants grow in damp soil just outside a pond. They’re good transition plants between land and water. Some tolerate completely waterlogged ground and others don’t, so check each plant’s needs before buying.

Water gardens are a joy to have in your garden, but they do require some maintenance. Here’s how to keep your pond healthy and attractive:

– Remove debris often. Use a skimming tool (available at nurseries and pond stores) to remove debris from the water surface. This will mean fewer toxins in the water and cleaner water for your plants and fish. In fall, screen your pond to prevent fallen leaves from adding too much organic matter to the water.

– Tend to water plants. Prune and divide as needed. Add either organic or chemical fertiliser to potted plants about once a month. Tablet forms make it easy to place fertiliser in the soil.

– Leave bacteria alone. The bottom of your pool, the surface of rocks, and the base of plants all provide places for healthy bacteria to live. They eliminate toxins in the water, so don’t scrub these areas. If you see long algae growing, though, take it out.

– Introduce natural bacterial enzymes. These products break down organic matter quickly. Purchase at pond stores and nurseries.

– Avoid overfeeding fish. Excess food floats in the water and breaks down into nutrients that feed algae. Feed fish once a day in spring, summer, and fall, when the water is warm. (They don’t need food in winter because they can’t digest food in cold water temperatures.) Give them only as much as they can eat in five minutes.

– Check pH, ammonia, and nitrite levels. Test a new pond quarterly; test older water gardens twice a year in spring and fall.

– Maintain equipment. Clean fountain heads and pump intake valves to keep them running properly. Check and clean mechanical and biological filters routinely.

What makes a pond ecologically sound?

Most water garden experts recommend creating a pond with an “ecologically sound” or “ecologically balanced” system—in other words, one that recreates nature as much as possible. Instead of requiring lots of chemicals or maintenance, an ecologically balanced pond stays healthy by relying on fish, plants, and microorganisms working together. It usually requires a mechanical filter and a biological filter and some sort of running water to circulate oxygen. It also needs a moderate amount of algae and beneficial bacteria to transform potential toxins into nutrients.


– Don’t add too many fish at once. A good rule of thumb for a new pond: one goldfish per 25 to 50 gallons of water.

– To keep algae under control, make sure 50 percent to 70 percent of the water is covered by surface-floating and deep-water plants in summer.

– You can build a water feature just about anywhere, but if you want to grow the widest variety of interesting water plants, make sure your pond is in full or part sun.


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