Ceratophyllum is a very good oxygenator and can grow to great depths so is ideal to put in lakes and ponds. It is a free floating plant but weighting helps secure the plant in the required location. Hornwort has foliage that resemble small horns from the Greek "Ceratos" (horn). Best weighted to secure the plant in the required location. Remove excess growth if necessary.
Only leaves that photosynthesise below the water surface oxygenate the pond. The best oxygenators are those whose leaves grow underwater, although all are a breeding site and shelter for wildlife. They remove nitrates, which helps reduce algae and keep water clear, meaning once established, many may be grown much deeper if light can reach them.
Pond Planet Oxygenator Guide:
Oxygenating planting depths are provided as a guide only, with the depth being the amount of water between the water surface and the top of the pond basket.
Weighed bunches can simply be dropped into the pond but would benefit from being planted in soil or gravel within a planting basket.
We recommend that 9cm oxygenating plants be potted up into a larger pond basket to allow room for growth. Make sure to position these smaller sized plants no deeper than 25% of the maximum recommended planting depth to allow the plants to mature.
It is not necessary to re-pot 1ltr oxygenating plants however it would be beneficial. Place this size of plant no deeper than 50% of the maximum recommended planting depth to allow the plants to establish themselves.
Given that 2ltr and 3ltr plants are larger and more established they do not require repotting, and can be placed up to the maximum recommended depth.