SRAC Publication No. 435
VI March 1999 PR
Water Gardens
Michael P. Masser*
Water gardens or garden pools Locating the water garden so that floating aquatic plants are provid- have become a popular part of it can be viewed from the house ed for shade. Water gardens that landscape architecture in the will increase your enjoyment and are at least two-thirds below United States. Water gardens are allow you to supervise it. Be sure ground level retain heat in cold visually soothing and seem to to control access to the water weather and are cooler in hot connect people to the natural garden to ensure the safety of weather. Those built totally above aquatic world. The esthetic value children. A good view of the ground may have to be drained of water gardens is enhanced by water garden will also help you during the winter and fish and the almost endless variety of spot unwanted visitors such as plants moved indoors. design and planting options that predators. Ponds can be built of several make each one a unique and per- Water gardens should not be types of materials. Some of the sonal creation. located over utility services. more common are earth, plastic Little formal research has been Check with utility companies for liners, fiberglass and concrete conducted on the ecology and the location of underground lines. (Table 1). Plastic liners are easy to management of water gardens, so Water gardens should not be install and come in a variety of most of the information in this located directly under trees shape and sizes. The lifetime of a publication was developed from because roots hamper excavation liner depends on the thickness related areas of research and prac- and may cause structural damage and type of plastic. tical observations. later. Also, leaves foul the water and over-hanging branches may Construction Water garden location, exude toxic substances into the Construction of a water garden size and type water garden. Consider the weight of the water before placing can be simple or complex. Water The location of the water garden a free-standing water garden on a gardens built of fiberglass or con- is critical to its ecology and main- patio or deck. Check structural crete take considerable construc- tenance, as well as to your enjoy- supports; water is very heavy. tion skill. Earthen and plastic- ment of it. Sunlight is needed for liner pools require less construc- The depth of a water garden tion skill or experience. Many plant photosynthesis. Plants are depends on design, local climate, important to the water garden’s commercial firms selling water and over-wintering strategies. garden equipment offer consult- ecology because they produce Many year-round outdoor water oxygen, remove and recycle nutri- ing services on design, construc- gardens have a section at least 3 tion and maintenance. Use avail- ents, and provide shade and hid- or 4 feet deep that does not freeze ing places for fish and other able expertise and your own cre- in the winter and gives fish a cool ativity to design a water garden inhabitants. A water garden retreat during hot weather. Large should be situated to receive at reflecting your imagination and koi carp, in particular, tend to lose taste. least 6 hours of sunlight each day. color and become stressed if they However, direct sun at mid-day do not have a cool place to stay Water gardens can be relatively during the warmest months can during hot weather. A depth of 18 expensive to build and maintain. cause shallow pools to overheat. to 24 inches is sufficient in the Cost of construction varies with deep south, as long as only a few size and the materials used, but *Texas A&M University. fish are stocked and plenty of can range from a few hundred Table 1. Typical construction materials for water gardens. Pool type Advantages Disadvantages Special considerations earthen inexpensive, especially seepage, wild plants may soil must have a high clay for larger pools become established content flexible liners ease of construction possible punctures, must be type of liner will determine pumped or siphoned to drain lifetime, usually 10 to 20 years fiberglass/plastic durable, long life shallow, not the best habitat very small pools could be for large fish, good for plants moved inside during the only winter, can crack if water freezes concrete very long life, can be expensive, can crack and may need to be coated with constructed with leak, must be cured epoxy or pool paint to stop decorative tiles leaching of minerals dollars to many thousands of dol- garden will concentrate fish dur- water by 1 to 2 inches help con- lars. Construction plans should be ing drainings and make it easy to ceal liner edges and hide pipes, reviewed by local governmental capture them. wires and equipment. The water agencies (e.g., Building and Rainwater run-off can cause prob- garden’s interior may be decorat- Zoning) to ensure that the pro- lems in excavated water gardens, ed with sand, gravel or rocks. posed pool complies with all so make sure that run-off water Much of the enjoyment of owning building codes. For example, all does not flow into the water gar- a water garden is in designing electrical service should have den. Run-off water can allow fish and landscaping the pool and the ground-fault interrupt circuits. to escape, introduce chemical con- surrounding area. Consider using Permits may be required. Water taminants, cause muddiness, and rocks of varying colors and gardens deeper than 18 inches may cause oxygen problems. If shapes, fountains, waterfalls, may be considered an “attractive the surrounding terrain is higher windmills, underwater lighting, nuisance” by insurance compa- than the water garden, a berm islands, bridges, and surrounding nies and may need to be within a may be required to direct run-off flower gardens. fenced area. Check with your water away from the garden. Some designers landscape around insurance company before con- Another problem can be rainwater struction. water gardens with arches, gates, saturation of the soil under the fences, and even gazebos to Water gardens may be irregular or water garden, which can cause it enhance their beauty geometric in shape. Irregularly to overflow or float out of the shaped water gardens have a nat- ground. To avoid this problem, Remember to level your pool ural look, while the geometric construct special drainage systems accurately! Otherwise, the water shapes appear more formal. under the pool. garden may end up with an exposed area at one end and Before you start construction, try Vertical sides let detritus (dirt, laying out possible water garden water about to overflow at the leaves, etc.) build up along the other end. designs using a garden hose or edge of the pool bottom, so sides rope. should be tiered and/or sloped to Water Before construction, plan where move detritus toward the deepest pipes, filters, water pumps, etc. part of the pool where it can be Quality will be located and how they will cleaned out. A common construc- be concealed. Plan where electri- tion method is to cut pool sides Whether your water garden is a cal and water lines should be into two or three tiers, each about plastic tub or an aesthetic wonder, placed for night lighting, pumps, 12 inches wide. Tiers help to hold good water quality is essential. fountains or waterfalls, and set liners in place and provide ledges Poor quality water makes the foundations for such structures as for plants and other decorative water garden less attractive and stepping stones, a walking bridge, items. can harm fish and plants. Once the basics of water quality are or the base of a fountain. Plan To protect a liner from being understood, maintenance will how the water garden will be punctured by roots and rocks, require a minimum of time. drained. Make sure the bottom firmly compact the dirt along the slopes so the water will drain to a pool sides and bottom and cov- The first consideration is a supply point where it can be siphoned or ered it with sand and/or old car- of good quality water to fill the pumped. Constructing a catch peting before installing the liner. pool. The most common sources basin (usually 6 to 12 inches deep) are city water and well water. Borders of flagstone, brick, or in the deepest part of the water Surface water from a creek or wood decks overhanging the Leveling the pond during construction.
A formal watergarden, fountain and waterlillies el. Water garden in a barr
Algae growth clinging to aquatic plants.
A less formal water garden with natural materials and an irregular shape. pond is not recommended as it concentrations (and remove because of plant photosynthesis may contain contaminants, dis- excess carbon dioxide). and respiration of plants and eases and wild fish, any of which Water garden nutrients come from other organisms. Fluctuation from may harm the water garden’s fish feed, wastes, decomposing 6.5 to 9 will not harm the water ecosystem. If city water is used it leaves and other types of organic garden’s ecology. A pH much must be dechlorinated before matter, and from fertilizers above or below this range will adding fish and plants. One week applied to pool plants. In a well stress or even kill fish. If the pH is of sunlight (or less, if aerated) will balanced water garden, plants will shifting above or below this dechlorinate city water if the chlo- remove nutrients rapidly and sup- range, you will need to increase rine source is liquid or gaseous press algal growth. If there are the water’s alkalinity to buffer chlorine. If the chlorine source is excessive nutrients algal growth is these fluctuations. Alkalinity can chloramine, it is best removed by stimulated. Pool algae can be fila- be increased by adding carbonates chemical dechlorination. Commer- mentous (stringy or hair-like) or such as agricultural limestone, cial dechlorinators made from planktonic (green water). Both oyster shell, or bicarbonate of sodium thiosulfate are available in types quickly become a nuisance soda. An alkalinity of more than liquid or pelleted forms from by clinging to plants, decorations, than 20 ppm is considered ade- aquarium and water garden retail- etc., clouding the water, and quate, but 50 ppm or more is bet- ers. restricting the view of fish and ter (see SRAC Publication 464). Water quality factors to consider plants. Dense algal growths can Water quality tests for D.O., are dissolved oxygen, ammonia, deplete oxygen at night or during ammonia, pH, alkalinity, and nitrite, pH, alkalinity, hardness, extended cloudy weather. chlorine can be purchased at most carbon dioxide, and contaminants Periodic algal blooms are part of water garden or aquarium suppli- or pollutants (such as pesticides). the natural cycle, particularly ers. It is a good idea to have test- These factors have different levels from fall to early spring when ing equipment available should of importance to water gardens. ornamental plants are not actively problems arise. For additional information on absorbing nutrients. Cleaning water quality see SRAC debris from the pool will help Filtration Publication 452. during these periods. If warm The water volume of the garden The amount of oxygen that dis- weather algal blooms occur, then must be determined before you solves in water (D.O.) is very over-stocking and over-feeding select a filter or pump, or perform small and is measured in parts per fish or over-fertilizing pool plants any chemical treatment. For infor- million (ppm or mg/L). The is usually the problem. Solutions mation on calculating area and amount of dissolved oxygen in a include increasing the number of volume of pools, see SRAC water garden can range from 0 pool plants, adding bio-filters to Publication 103. ppm to more than 20 ppm. remove excess nutrients, or flush- Oxygen dissolves directly into the ing water through the pool to Not all water gardens need filtra- water garden from the air if the dilute nutrients and disperse tion. Water gardens with lots of water is agitated by wind, water- algae. plants and a modest number fish should not need filtration. If a bal- falls, etc. Underwater plants also Ammonia is the major nitrogen produce oxygen as a byproduct of ance is maintained between the waste excreted by fish. Bacteria number of plants, the number of photosynthesis. The amount of decompose ammonia to nitrite. oxygen in the water will vary fish, and the amount of nutrients Ammonia and nitrite are both the water garden receives, then no with the amount of agitation, the toxic to fish but are seldom prob- numbers of fish and plants, the other filtration should be neces- lems in water gardens. These sary. However, keeping the proper time of day, and the water tem- compounds are normally perature. More oxygen can dis- balance is as much an art as a sci- removed from the water by pool ence. For this reason, many peo- solve in cool water than in warm. plants that use them as nutrients. As temperature increases in the ple become frustrated and opt for Ammonia and nitrite can become additional filtration. summer, fish increase their metab- problems if fish are over-fed, olism, less oxygen can dissolve in plants are over-fertilized, or There are two types of filters— the water, and respiration from organic matter in the garden (e.g., mechanical and biological. decomposition is highest. All of leaves, dead plants, fish, etc.) Mechanical filters remove or trap this can lead to low dissolved decomposes rapidly. Excess particles of dirt and organic mat- oxygen, particularly at night ammonia and nitrite can be ter. Leaf skimmers, foam filters, when underwater plants are also removed by biofiltration (see and settling basins are the most using oxygen in respiration. Fish Filtration section), by flushing, or commonly used mechanical filters will become severely stressed at by adding bacterial water condi- in water gardens. Sand filters and D.O. concentrations below 3 ppm tioners. cartridge filters like those used in and will die at a D.O. concentra- swimming pools or hot tubs are tion of about 1 ppm. Mechanical The pH of water is measured on a not recommended for water gar- aeration from waterfalls or foun- scale from 0 to 14, with 7 being dens because they clog quickly tains can maintain minimum D.O. neutral (<7=acidic, >7=basic). and are difficult to keep clean. Water garden pH changes daily Biological filters remove excess Fish (Top exhibitors in Japan stock nutrients from fish wastes, fertiliz- only 10 to 15 koi even in large ers and decomposing organic mat- Stocking rate water gardens.) ter. Bacterial bio-filters are popu- One common mistake is stocking lar for water gardens, particularly too many fish. A water garden is Types of fish those in which fish are the major suitable for fish only as long as it Fish most commonly stocked in attraction. Bacterial bio-filters con- can supply adequate oxygen and tain layers of gravel or coarse water gardens belong to either the decompose the wastes produced. goldfish or the koi family. There sand, plastic sheets or rings, mesh The number of fish the water gar- or foam, or some other material as are numerous varieties of these den can support depends on fac- fish. a substrate on which bacteria tors such as the size of the water References to goldfish are found grow. Bio-filters operate best in a garden, size of the fish, tempera- in Chinese poetry as early as 1,000 pH of 7 to 8 and an alkalinity of ture, amount of sunlight the A.D. The Chinese and Japanese >50 ppm. Adjustments of pH and water garden receives, whether or nobility developed many of the alkalinity can make bio-filters not aeration is provided, and how varieties we see today from the more efficient. Bio-filters require well the natural or artificial filtra- original wild form. Today there little maintenance if properly tion system removes wastes. The are many varieties to choose from. designed. following examples give stocking Varieties with normal body struc- Under-gravel filters, common in rates recommended by fish hob- tures are best for water gardens. aquariums, are one of the simplest byist magazines. These would include common types of bio-filters. The gravel acts First, determine the water gar- as a mechanical filter and is colo- goldfish, shubunkin (or calico), den’s surface area in square feet. comet, and fantail. Varieties of nized by bacteria. Large gravel fil- An unaerated water garden can ters can be built into the water fancy goldfish such as the nymph, be stocked at up to one 12-inch fringetail, veiltail, lionhead, curled garden bottom or constructed as a fish (not including the tail) per 4.5 stream bed outside the garden. gill, and bubble-eyed goldfish are square feet of surface area. If the not well suited for outdoor water Water is pumped from the pool water garden is aerated with over the gravel bed and back to gardens because they are more fountains or waterfalls, then stock vulnerable to predators. the pool. The problem with gravel up to one fish per 2 to 3 square Koi carp are descendants of the filters is that they become clogged feet. (Conservative water garden European common carp (Cyprinus with solids and require laborious hobbyists suggest stocking only 6 carpio). Koi is a Japanese word cleaning. inches of fish per 5 square feet of meaning “love” and koi giving in A common type of in-pond filter surface area or 8 to 12 inches of Japan has much the same mean- uses plastic media and foam sur- fish per 16.5 square feet of surface ing as flower giving in the West. rounding or connected to a sub- area.) Koi have been bred in Japan since mersible pump. It acts as both a For example, if a water garden mechanical and a biological filter at least 300 A.D. and are a popular measures 9 feet by 15 feet, the ornamental fish because of their (Fig. 1). The pump draws water surface area is 135 square feet. through the filter media, trapping wide variety of colors and color Dividing 135 square feet by 4.5 patterns. Each color and pattern sediment and providing an area square feet (per 12 inches of fish) for bacteria to grow. With this combination is given a distinctive equals 30 units of 12 inches or 360 Japanese name. Prized koi have type of filter, sediment must be inches of fish total. The average removed periodically and the bright, intense colors, sharp color adult koi carp is 18 inches long, so definitions, and distinctive foam cleaned frequently. Other this 9 x 15 foot water garden can bio-filter designs can be found in arrangements of markings. Koi support 20 adult koi carp (360 with exceptional coloration and aquaculture and water garden inches ÷ 18 inches each = 20 fish). publications. patterning can be valued at thou- sands of dollars. Koi can grow quite large and sometimes live for Return to waterfall (Side view) 60 or 70 years. These fish can truly or fountain be lifelong pets. Plastic container Acclimating the fish at stocking