Building a Successful Koi Pond Water Garden

Koi with water lily

The idea of a koi pond and water garden for many years was a concept that did not go together. Japanese koi have had a bad reputation of destroying plants in a water garden and the idea of putting them together would be a disaster. The traditional koi pond was much deeper than a water garden and required large biological and mechanical filters to keep the water clean. UV sterillizers were used to kill free floating algae and parasites and plants were out of the question. In order to combine the water garden and koi pond, we must first understand the eating habits of koi. Koi are omnivorous, meaning they eat both plant and animal matter. Their whiskers help them to forage through the rubble and substrate to find food. As the water temperature increases so does their appetite and the summer time their metabolism is at a peak and they will feed none stop.

Bottom Drain To Skimmer

When designing a koi pond water garden there are a few things to keep in mind. The deeper the pond is the larger the koi will grow. Koi can grow up to 30" and they need room for this to happen. A typical koi pond should have a deep section at least 3 feet and 4 to 5 feet is better. The deep section should be 30 to 50 percent of the total area of the pond and not have any gravel. Adding a bottom drain to the deepest part will keep the bottom free of sludge build up. The bottom drain can be plumbed to the skimmer in front of the mechanical filter. Simply drill a hole in the skimmer well below the water line in front of the mechanical filter and add a bulk head fitting. The water will be drawn from the bottom drain by gravity as the pumps runs. The pond skimmer should be at the deep end and pump water to the opposite shallow end preferably to a waterfall or stream. A waterfall or stream will add oxygen to the water by breaking the water surface. When constructing a stream lined with gravel be sure to add at least 2 feet on both sides for the liner. This will make it easier to keep grass clipping out of the water. The gravel will act as biological filter and allow for plants like watercress to help filter the water. The watercress is also a great food source for the koi and has almost all the same vitamins and minerals of spirulina algae. Water flow for the koi pond water garden should be .5 - 1 times the total gallons of the pond per hour. For example, if the total gallons of the pond is 3,000 gallons the water flow should be 1,500 - 3,000 gallons per hour.

Make large flat shelves for water lilies and shallow water plants with steep drop offs. Shelves for water lilies should be 2 - 3 feet wide and filled with 2 - 4 inches of 1-2 inch gravel. The ideal depth of hardy water lilies is 1.5 - 2 feet. Line the edge of the shelf with medium to large flat rock. This will keep the gravel on the shelf as koi will move the gravel around as they forage for crustaceans. The hardy lilies should be taken out of the pot with the roots rinsed clean. Simply bury them in the gravel and make sure the tuber is covered by 2 - 3 inches of gravel. You can add fertilizer tablets when they are planted. The root structure will expand out as far as the lily pads and you will never have to fertilize them again. Make shallow shelves for water iris about 4 - 6 inches deep. Again line the shelf with medium to large flat rock and take the plants out of the pot and plant them in the gravel. Plant watercress on a shelf in 2 -3 inches of water and place boulders around the the plant as a barrier. The boulders should extend 2 -3 inches above the water line to keep the koi out. The watercress will grow over the rocks and allow the koi to feed on it without destroying the roots.

A koi pond water garden creates beauty and looks more natural. The plants give the koi shelter and food and help remove fish waste from the water making it easier to have crystal clear water without very large mechanical and biological filtration. Having gravel on the shelves and shallow areas provide a habitat for ghost shrimp, worms and other crustaceans for koi to feed on. A waterfall or stream adds oxygen to the water and also creates a pleasing sound. So what are you waiting for? Isn't it time to create your own koi pond water garden?