Pond Plant Spotlight: Anacharis & Hornwort

Anacharis and Hornwort are oxygenating vegetation, which means that they play an essential role in ponds, especially those that don’t use many filters or pumps. Experts recommend planting the two together, because although they are distinct, they provide benefits which are alike. Anacharis and Hornwort are considered the best plants in the wild when it comes to the filtration of water as well as oxygen generation.


Anacharis is a hardy plant that grows rapidly during summer and spring. It is prized for its ability to behave like a filter and pump. Their growth will slow down during fall and winter until they finally go dormant until spring.


Hornwort is also a productive plant, but grows best in shade and should never be exposed to direct sunlight. It appears in clusters and will occasionally grow together with Anacharis which gives it additional shade. Hornwort does not root to the bottom of the pond.

How To Introduce These Plants

This plant duo is simple to introduce to ponds, making them ideal for beginners. Hornwort can be tossed in and it will gradually sink. Rain will also contribute to this process. However, one must exercise caution, as these plants are susceptible to overgrowth. Periodically you will want to clip the Anacharis or even remove a bit of hornwort completely.

Anacharis will take root in deeper pond areas, and will extend outward. Sometimes it will hug the embankment edge, but not always. If you find that these plants have grown excessively, a wise choice is to remove some and then sell the excess to a nearby pet or floral shop. Selling the extra vegetation is much wiser than throwing it away.

How Plant Oxygenation Occurs

Oxygen gains entry to pond water via plants within it and the surrounding atmosphere. It can also gain entry through rain and wind. For plants, the main oxygen sources are derived through algae which is microscopic and vegetation which is submerged. It is also possible to acquire oxygen through sunlight in the form of photosynthesis. It is by this method that Anacharis and hornwort place oxygen in pond water.

During evenings, plants extract oxygen from pond water via respiration. During the day they will generate greater oxygen than is consumed. As a result, fish and other pond animals get the oxygen they need, which shows that Mother Nature provides a good balance, but not always.

Why Things Sometimes Go Wrong

One common reason fish kills occur in ponds is because of oxygen depletion. The phenomenon is most frequently seen in summer since warmer water contains less oxygen than water which is cool. The demand for oxygen is higher in water that is warm, and if the levels drop too much, the largest fish will die off first. Fish which are smaller and or tough are more resilient, as are some amphibians. This is why having quality pond aeration is so important. There are certain plants whose presence also depletes oxygen levels, most notably duckweed.