Koi Pond Plants

Watercress in early fall Watercress in early spring

It is true that Japanese koi eat plants. When the water temperature is above 70° F koi have an enormous appetite. Since koi do not have a stomach they don't eat very much at one time. They are naturally bottom feeders and constantly sift through the bottom rubble for food. Having pond plants in a koi pond will provide shade, cover for the koi from predators, a good food source, and also increase the biological filtration. Since the plants will feed on the nutrients from the fish waste, they help keep the water quality good and the water clear. Water plants also harbor small crustaceans such as ghost shrimp that the koi will feed on.

It is much easier to have plants established in the pond before adding koi. The larger the koi, the more destruction they can do on the plants. If there is not any gravel on the bottom of the pond, adding a potted plant to a pond is like ringing the dinner bell for koi and they can uproot the plant in a short time. The best way to keep koi and plants together is to have gravel in the bottom. You do not have to gravel the whole bottom. If there is a bottom drain its is best to leave 30% where there is no gravel in the deepest part of the pond. Use large rocks and boulders to keep the gravel in the more shallow areas. Plants will grow better and look more natural if taken out of the pots and planted directly in the gravel. It is always best to have a plant that the koi enjoy eating and provides good nutrition. This will tend to keep them from destroying water lilies and other ornamental plants. Water celery and watercress both contain significant amounts of iron, calcium and folic acid, in addition to vitamins A and C, and koi love it. Watercress does better in fast moving water such as a stream bed or under a waterfall. Both of these plants will have to be barricaded from the koi. The use of large rocks and boulders will protect the plants and the koi will eat what grows over the barrier.

Hardy marginals like water iris, pickerel rush, and arrowhead give a good contrast to the waters edge and give a natural look to the koi pond. Adding plants to a pond that has koi 10" or larger can be a bit more challenging. Adding the rock work, gravel and marginals first will aid in adding water lilies later. Plants like water iris and pickerel are not normally eaten by koi and may do just fine without any protection, while watercress and water celery will need some protection even after they have become established. A whole area may have to be barricaded to protect water lilies until they are established. A minnow seine net would work well for this. They have weights on the bottom edge and floats on the top to keep the koi out of the planted area. Once the roots become established the seine net can be removed.

Pickerel Rush Variegated Sweet Flag Colorado Water Lily Water Celery