Hornwort (Ceratophyllum demersum), a submerged water plant helps fight against green water, the one thing alot of pondkeepers may tend to fight. They are important to water quality and water clarity. They help to filter out the unwanted nutrients and add the important oxygen to the pond water during the day. Hornwort is one of the submerged plants or sometimes referred to as "oxygenator" because it add oxygen to the water in the pond. During the night the submerged plants revert the process and remove oxygen from the water. Hornwort produces small flowers that often bloom in the late spring or early summer and often throughout the summer and are submerged with the leaves under water.
Hornwort prefers full sun and as other submerged plants plays a vital role in creating and maintaining an ecosystem that is suitable for your wildlife and fish. Hornwort, through photosynthesis draws nutrients through its leaves as well as its roots. Hornwort is considered to be one of the best cleaners. It can even be pulled from your pond and rinsed to clean its leaves and returned to the pond ready to collect more dirt.
Hornwort is an excellent spawning ground for fish in the spring to mate and lay their eggs. You can pull the hornwort out and lay it into another area to raise the fry if you want. Because hornwort is of a course texture, the fish tend not to eat it.
The questions always rises as to how many is adequate for my pond? You can never have too many unless you have a small pond and then it can cause rapid pH swings from day to nights because of their oxygenating properties. For most lined ornamental ponds you need about 10-15 bunches of oxgenators for every 10' by 10' area that is 2'-3' deep. But it depends on your depth. If your pond is mostly around 6 inches deep with a small deeper part, then start with a few and add.
A well balanced pond depends on submerged plants. It is best to plant hornwort in a pot. Use one that is shallow and wide. You can also plant it in with another plant such as a lily or lotus.
A great start in the spring is adding your submerged plants after your general cleaning of your pond.