Koi

To say koi are just colorful carp is to miss the rich history of these fascinating fish. Almost two hundred years ago colored mutations were seen in the black carp that the Japanese were eating for food. Several color patterns were developed in the late 1800s, but improvements in color and new color patterns were developed in the Niigata Prefecture region of Japan from the 1930s to the 1970s. The search for the perfect koi is still going on, but now there are also breeders in the U.S., South Africa and Israel.

Of the more than forty common color patterns, the three preferred color patterns are Kohaku, which has a white body and a red pattern, the Sanke, that is white with red and black on it, and the Showa, a black fish with red and white on it. Platinum white and lemon yellow fish are found in most people's ponds, partly because they stand out well against the dark bottom.

Koi can easily grow to two and one half feet long and be as big around as a loaf of bread. Some will grow to over three feet long and be as big as a watermelon. Koi can live several decades and some live over one hundred years. Future ownership plans may need to be in someone's will.

Just like there are dog and cat shows, there are koi shows. The owners carefully take the fish out of the pond and to the show where it is placed in a large blue vat. Judging is based on a point system that awards good body conformation first. Color quality is next and color pattern third, with some judge's discretionary points last. Fish with good conformation that have reached a mature size and still have high color quality can be rather valuable. Award winning, two foot long koi can easily cost twenty thousand dollars.

A client who wants to maintain a couple dozen high quality koi in a pond will expect the pond to meet the needs of the fish. Not all large koi are valuable, the non-winners will also grow up, but their owner will still want to see them thriving in healthy water. Individual koi have personalities and are often very friendly fish. They can be trained to eat out of the owner's hand and may even be petted.

Koi Pond Design Considerations

Koi breeders and wholesale distributors often grow the fish in large mud bottom ponds. These ponds are filled with algae and microorganisms. The fish thrive and grow in size and often develop much better color in these ponds. Even though the fish do fine, they are not visible and this is not what your client wants when they ask for a koi pond.

Koi pond design is based on fish health concerns, site conditions, climate and budget. There isn't one pond or filter design that will meet all the needs of every situation. There are several differences between a koi pond and a water garden. Both of these man made water features need mechanical and biological filtration, koi ponds however, are typically devoid of plants and rocks or gravel, giving them less ability to stay ecologically balanced. Koi ponds are deeper, wider and have more external filters than typical water gardens. Water gardens often have rocks and gravel for naturalizing plants and protecting the liner.

Koi ponds can be looked at as being large outdoor aquariums, designed to be viewed from the top instead of the sides. Most are without plants or any other obstructions to the view. Because of the large size of some koi and the over stocking of many koi ponds, any plants would be nibbled to death in a short time. In a koi pond, fish are the focal point. In a water garden, the entire setting of moving water, plants, fish and the dry land plantings are all designed to be part of the view.

To help protect koi from predators and add more water volume, koi ponds are usually built with vertical side walls that drop down several feet. There are usually no plant shelves along the shoreline, since plants are not the main focus. Water gardens usually have several steps for planting various shoreline plants. The maximum depth in a koi pond is at least four to six feet and ten or more is not uncommon. Deeper ponds promote more muscle mass and better fish health as the fish can swim through greater water depths. Water gardens rarely are deeper than two feet.

Larger ponds give the fish more space to swim in and more water means greater chemical and temperature stability. In most koi ponds the narrow side is at least a minimum of ten feet wide. Ponds with curvy bays and peninsulas will need additional water circulation jets.

Having some of the filtered water return back to the pond through side jets helps to create a current. The current forces the fish to swim and exercise and if angled properly it will send debris to the mechanical filter or skimmer.

When plants are used, they are often supported on pedestals to raise them up out of harms way. Shoreline plants that have roots in the water and leaves above, provide shade and hiding places for the fish. Design accent plants into the pond to create a focal point. Combinations of foliage texture and color work well. Most shoreline plants have vertical leaf or branch structures, providing good contrast with the horizontal plane of the water.

Because of the straight down sides and deeper depth many koi ponds are built out of concrete. In the past, they tended to be of a formal shape. Newer construction methods are allowing more creativity in design. Oriental style ponds are very popular, partly because America's fascination with Oriental landscaping in general and partly because the koi originated there.

Flexible rubber liners are common in water gardens and, because of its much lower cost than concrete, it is becoming the liner of choice for many koi ponds. Creating a stable edge between water and land is very important for any pond. Koi entice people to come right up to the edge of the pond to see them. Without shallow steps along the edge, koi ponds can be as dangerous as the deep edge of a swimming pool. Not only is a stable edge important, but so is the creation of a visual edge that separates land and water.

Fountains are occasionally added to help with water circulation. Ponds with expensive fish rarely have anything in them that would allow a fish to get scratched, thereby lowering its value.

Shade structures are often used in warm climates to shade the pond. It keeps the water cooler, hides the pond from predators and helps the fish retain their color. In the hot sunny microclimate of a patio, a shade structure reduces glare and makes the patio more useful.

Filtration

A typical koi pond filter system will include the following components. Bottom drains and surface skimmers to remove debris laden water from the pond. Settling tanks or filter nets and pads to remove large debris. Biological filters to remove invisible chemicals like ammonia and nitrite. Ultra-violet lights and ozone generators are sometimes added to kill algae cells and bacteria.

Bottom drains are used to pull bottom water from the pond to create a full re-circulation system. They also are designed to remove debris that sinks to the bottom. In deep koi ponds it is harder to remove leaves with a net than it is in a shallow water garden, so it is easier to have the bottom drain remove settled debris. Air bubblers can be installed above the bottom drain cover to create an upward flow. This flow pulls water across the pond bottom to the drain.

Most koi pond filters are gravity fed. This allows the debris to be caught in a skimmer or settling tank, before the pump has a chance to grind up the debris. Settling tanks have drains of their own so they can be cleaned regularly. The downward gravity flow to the tanks from the pond bottom and then from the tanks to the drain can be difficult to arrange on flat sites.

Many koi ponds use external 'dry' pumps rather than submersible pumps. These in-line pumps provide high flow volumes while often being more energy efficient than submersible pumps. Higher flow rates gives the filters more water and gives the fish a stronger current to swim in.

Once the water is past the pump, it is often sent through an ultra-violet light before going on to the biological filter. The light helps to kill algae cells and may kill disease-causing organisms if sized correctly. The biological filter can be a pressurized canister with filter media or it can be a large tank containing filter media. Some tanks are designed to look like a natural spring and waterfall. Bacteria grow on the filter media and consume the toxic chemicals.

Ozone is sometimes used after the biological filter. It oxidizes any remaining parasites or disease organisms. It quickly disperses in the pond, but not before it helps to reduce algae and improves water quality. It does not promote ozone in the atmosphere.

After the pond is dug, there may be little room left for the large filters. Since the filters would detract from the view, berms, shrubs and ornamental grasses are often used to hide them. In some cases, small buildings are built to help hide the filters.

Some koi pond owners get the best of both worlds when they use a water garden as part of the biological filter system. They plant water plants as filters in the upper pond and the filtered water flows down to the koi pond.

A hybrid koi pond and water garden can have a few koi and some goldfish and lots of plants. It has many of the features of a water garden, but is bigger. It is not designed for keeping show quality koi.

The next time one of your clients asks about putting in a koi pond, you can tell them that koi ponds are better suited to koi health than water gardens. They handle the larger pollution loads better and provide the best protection from predators. On the other hand, they are also more of a safety hazard to people, pets and wildlife. They cost more to install and have hard to hide filters. lasn

Jeff Rugg MLA, ASLA

With degrees in science, zoology, horticulture and landscape architecture, Jeff uses his many interests to help others learn about nature. He has managed garden centers in Texas and Illinois and owned a water garden and wild bird nature store. His weekly newspaper column 'A Greener View' has been well received for many years. His articles and photographs have also appeared in Pond Keeper, Water Garden Magazine, Landscape Contractor Magazine, Ponds USA and other publications. Photography by Jeff Rugg and Gary Wittstock, Pond Supplies of America - except those of Hakone Gardens taken by David Harlon Cade.