Choose Right Plants for Koi Pond

With Spring arriving many koi hobbyists will enjoy adding plants to enhance their koi pond environment, but some are unaware of the dilemma adding the wrong plant inside the pond could cause the koi to get ill and worse die.

An overabundance of aquatic plants can also strain a pond’s ecosystem and potentially lead to a fish kill. During daylight hours, plants produce oxygen and raise the water pH, yet at the same time the plants respire, removing oxygen and adding carbon dioxide and lowering the pH. 

Dead leaves will also rot and create waste products in a pond, so yes, they will eventually harm fish. However, that depends on how big the pond is vs how many leaves are in there.

Pond experts recommend covering no more than 50% of the pond with plants to aid in providing shelter for the fish and reducing excess nutrients. This also limits algae growth and moderates water temperature on hot days.

Please use this reference chart when selecting plants close or at your pond site, this chart is courtesy of

Toxic Plants to AvoidToxic Plants to Avoid
Allamanda – all partsJack-in-the-pulpit – all parts
Aloe – leavesJapanese laurel – all parts
Alocasia – leaves and stemsIndian Turnip – all parts
Allspice – leaves, seeds Iris – leaves, roots, rhizomes
Amaryllis – bulbsJasmine – berries
Anemone – all parts Java Bean – uncooked bean
Anthurium – all partsLantana – all parts
Apricot – leaves Larkspur – all parts
Azalea – all partsLaurel – all parts
Baneberry – berries, rootsLily of the Valley – all parts toxic to cats
Bird of Paradise – seeds Lobelia – leaves
Black Locust Bark – sprouts, foliageLocust – bark, leaves, seeds
Black walnut – all parts confirmed reports of deathLocoweed – all parts
Boxwood – leaves, stemsLupine – all parts
Buttercup – sap, leavesMarijuana – all parts
Cactus Mayapple – all parts
Calla Lily – leavesMimosa – all parts
California tern – roots, seedsMistletoe – berries
Cardinal flower – all parts but I have not found that to be true Mock Orange – fruit
Carolina jasmine – all partsMorning Glory – all parts
Caladium – whole plantMustard – roots and seeds
Cherry – bark, twigs, leaves, pitsNarcissus – bulbs
Chenille plantNightshade Oak – acorns, foliage
Choke cherry – all parts I do have reason to believe that this plant MAY be toxic to fish from correspondence with ponder who lost a lot of fish that ate the cherries that dropped in her pond. Use caution when placing a pond under this tree.Oleander – all parts
Colocasia – all parts I have several different varieties in my pond and my koi do chew the roots.  I have not had a problemPeach – leaves
Coral Plant – seeds Philodendron – all parts
Croton – seeds Pine – sap
Daffodil – bulbsPoinsettia – leaves, flowers
Datura – all partsPotatoes – eyes, new roots
Day lily – very poisonous to catsPrivet – berries, leaves
Delphinium – all partsPrunus varieties – seeds, some parts
Death Camas – all parts Ranunculus – all parts
Dumbcane (dieffenbachia) – all partsRedwood – sap (from decks also)
Digitalis – all parts Rhododendron – all parts
Easter lily – very poisonous to catsRhubarb – leaves
Elephant’s – ear all partsSnapdragon – all parts
Eggplant – all but fruitSnowdrop – all parts
English Ivy – all parts  confirmed reports of death Taro – all parts
Foxglove – all partsTiger Lily – all parts, especially to cats
Gloriosa lily – all partsTomato – leaves
Hemlock – all partsTrumpet vine – all parts
Holly – berriesTulip – bulbs
Honeysuckle  I have  a reported case of fish deaths after eating the flowers and leaves.  Once the leaves and flowers were removed from the pond, and the water changed out, the fish stopped dying.
Hyacinth – bulbs

So now that you know which plants to keep away from the koi, you may be asking yourself which plants you could have inside or near your pond.  My research found the following acceptable water plants that are safe for the koi fish and add beauty and oxygen to the koi pond environment:

  • Water Hyacinth
  • Water Lily
  • Lotus
  • Water Iris
  • Water Poppy
  • Water Smartweed
  • Duckweed
  • Umbrella Palm
  • Elodea
  • Fanwort

Remember to use only 50% of pond for any water plants and to keep them under control so they do not overwhelm the pond.  Plants help provide shade for the koi which in turn will help control the pond water temperature, as well as provide additional oxygen the koi need.

So, feel free to add plants to your koi pond oasis, just remember to research the plant and make sure it does not hurt the koi inside the pond, and enjoy the koi and the plants together in harmony.