Pond Plants 5: Oxygenating Plants
by Mandy Anders
Plants release oxygen as a byproduct of photosynthesis. Oxygen releases through microscopic openings called stoma. The majority of stoma are located primarily in leaf surfaces (although to a lesser degree they are present in stems as well). For pond plants, this means that submerged leaves produce oxygen directly into the water, increasing O2 levels in ponds. For the health of fish and other pond organisms, the ideal level of dissolved O2 in ponds is between 8-14 ppm. Oxygenated water is also less likely to house mosquito larvae than stagnant water.
Submerged pond plants produce O2 in the presence of light, providing a useful boost to pond oxygen levels during the hot, sunny days of summer. Additional oxygen should still be provided by circulation pumps, such as Sicce Dirty Water Pumps and other Syncra pond pumps, and/or Danner air pumps due to oxygen levels fluctuating throughout the day and plants consuming oxygen at night.
Oxygenating pond plants can grow either potted or floating in the pond. If potted, simply anchor the plants in pea gravel or pond potting media. Broken stems continue to grow and can be planted or just allowed to float throughout the pond. Be aware that floating stems can clog skimmers, bottom drains, and small pre-filters.
Several choices in oxygenating plants are available and can be grown singly or in conjunction with one another. Each of these varieties can overwinter in most planting zones if moved to the deepest area of the pond during the winter months. The most common oxygenating plant is Anacharis.
Anacharis” Egeria densa is the older scientific name for this genus and several other aquatic species. The species of Anacharis sold for water gardens is also called Brazilian Waterweed and is native to South America. This dark green, feathery plant SHOULD NOT be confused with the similar-looking invasive plants Hydrilla or Elodea canadensis. Egeria densa is not typically invasive in North America. Another variety of Anacharis, narrow-leaf Anacharis Egeria najas, is also native to South America. It has brighter green, thinner leaves than the common Anacharis. Both varieties of Anacharis will grow in ponds up to 36” deep.
Cabomba Cabomba carolinia is a green to purplish green feathery plant native to North America. It is typically grown in both ponds and aquariums. Hornwort Ceratophyllum demersum, also called coontail, is native to North America. This brushy plant grows best floating in the pond. Ludwigia Ludwigia repens, native to North America, has both a submerged and emersed (above water) plant form. The submerged form will grow the same as other oxygenating plants, but the emersed form should be planted like a bog plant.
For more information about oxygen in ponds and aquariums:Emergency Oxygen for Koi Ponds
The Importance of Dissolved Oxygen