Pond Plants That Help

One of the best plants for a koi pond. Water hyacinth floats freely on the surface, trailing long roots that absorb nitrates and phosphates directly from the water — making it a natural filter. It grows rapidly in summer and produces beautiful purple flowers. Koi will nibble the roots but rarely destroy the plant entirely. Note: water hyacinth is invasive in warm climates and should never be released into natural waterways.

Similar to water hyacinth in its water-purifying abilities. Water lettuce forms rosettes of velvety pale green leaves and trailing roots that koi love to pick at. It provides excellent shade in summer, which helps reduce algae and keeps the pond cooler. Like water hyacinth, it is invasive in warm climates and should be disposed of responsibly.

The lotus is the crown jewel of pond plants. With enormous round leaves that repel water and stunning flowers in pink, white, and yellow, a lotus in full bloom is breathtaking. Koi generally leave lotus roots alone once established, though they may nibble young shoots. Lotus need full sun and warm temperatures to bloom and go dormant in winter in cooler climates.

Water lilies are the most practical plant for koi ponds — their floating pads shade the water, reducing algae and providing shelter for fish. Available in hardy varieties that survive freezing winters and tropical varieties for warmer climates. Koi will eat water lily pads, which can frustrate keepers, but established plants usually produce leaves faster than the fish can consume them.

Hornwort is a fully submerged oxygenating plant that grows rapidly and absorbs nutrients from the water column. It provides excellent cover for small fish and a natural surface for beneficial bacteria. Koi may nibble hornwort but rarely eradicate it due to its fast growth rate. Simply drop bunches into the pond — no planting required.

Marginal irises planted around the edge or in shallow areas of the pond add height, structure, and seasonal color. Yellow flag iris and Louisiana iris are particularly well-suited to pond margins. Most iris varieties are unpalatable to koi, making them one of the more reliably unkibbled pond plants.

Plant in mesh baskets filled with heavy clay-based aquatic compost — never regular garden soil which will cloud your water.

Top baskets with pea gravel to stop koi rooting in the compost and disturbing the soil.

Aim for floating plants to cover 30–50% of the pond surface in summer — this shades the water, reduces algae, and provides refuge for fish.

Remove fading leaves and flowers promptly to prevent decomposition from adding nutrients back to the water.

Divide plants every 2–3 years to keep them vigorous and prevent overcrowding.