No one likes a stagnant, smelly pond. Whether you’re sprucing up your koi pond or maintaining the summer’s favorite swimming hole, oxygenating pond plants can improve your water’s overall health and appearance.
Read on to find out how. Plus, check out a few recommendations for which oxygenating plants are best for your pond.
What Are Oxygenating Pond Plants?
Oxygenating pond plants are plants that grow partially or entirely underwater. During photosynthesis, these plants release oxygen into the water. They also provide many other benefits (detailed in the next section) and can make an attractive addition to your waterscape.
There are four types of oxygenating pond plants: bog, floating, marginal, and submerged.
Bog plants enjoy bog-like conditions where they can access damp soil without much standing water. They do best around pond edges where only their roots will contact water.
Common bog plants include pitcher plants and some species of rhubarb.
Floating plants float on the water’s surface. Their roots do not require soil. Duckweed, water hyacinth, and water lettuce are floating plants frequently found on ponds.
Marginal plants live on the edges of ponds where they can access both soil and water. Also called emergent plants, they thrive in water no deeper than six inches above their crown (the part of the plant not in the soil).
Part of the plant exists in the water, providing some oxygenation benefits. Some of the most famous pond plants – cattails, lotuses, rushes – are marginal plants.
Submerged plants, as their name suggests, grow entirely underwater. This growing position means they release oxygen directly into the water, making them the best oxygenators of these four types.
Some submerged plants have features, such as flowers or leaves, that live above the water surface. You might also hear these plants referred to as macrophytes or submersed plants. Common submerged plants include anacharis, eelgrass, and hornwort.
Like plants rooted in dryland, pond plants can be either perennial (also called hardy) or annual (also called tropical).
Benefits of Oxygenating Pond Plants
Oxygenating plants are key to clear, healthy pond water.
Fish require dissolved oxygen to survive. In fact, ponds need to maintain an oxygen level of 6 parts per million (ppm) to support most aquatic life. Most species of fish will die at oxygen levels below 3ppm.
Oxygen enters the water through the atmosphere. But certain plants also contribute to this oxygenation. During photosynthesis, these plants absorb carbon dioxide and release oxygen directly into the water.
This function means that oxygenating pond plants serve as a natural alternative to an oxygen pump. Although oxygen pumps perform a crucial function, they can sometimes harm fish and other pond wildlife.
In addition to oxygenizing the water, these plants can significantly reduce algae growth in your pond. Nitrogen is an essential nutrient for plant life, so it’s no surprise that algae thrive in ponds containing high levels of this mineral. In isolation, algae growth isn’t harmful. But when it spreads, an algal bloom can block out sunlight necessary for submerged and floating plant growth.
This blockage will reduce oxygen levels in the water, potentially harming or killing aquatic life. (Plus, it’s not very fun to swim through an algal bloom on a hot summer’s day!)
Oxygenating pond plants are a natural filtration system. They absorb minerals such as nitrogen from the water, making it less available for algae.
If your pond is at risk of nitrogen runoff (from agricultural fertilizer, manure, sewage effluent, or other industrial sources), consider planting some oxygenating pond plants to prevent the spread of algae and other aquatic imbalances.
Oxygenating pond plants provide fish with shade, protection, and an area to spawn. These plants can also house frogs, newts, and insects. Pond plants with flowers above the water’s surface also support pollinators.
Plus, they can add decorative appeal above and below the pond’s surface.
How to Plant Oxygenating Plants in a Pond
Step 1: Select a Location
The size of your pond will determine which type of plants will grow successfully in its waters. Consider factors such as water depth, surface area, and soil availability around the pond edge.
Planting a mixture of bog, marginal, floating, and submerged plants will increase your pond’s biodiversity.
However, too many plants per square meter of water can negatively impact the pond’s overall health. (The ideal amount is about three plants per square meter.)
Step 2: Gather Materials
To plant pond oxygenizers you will need an aquatic basket (also known as a pond basket), compost, and your chosen plant.
In most cases, you’ll need a pond basket to plant pond plants. A pond basket anchors the plant, keeping the plant from floating away to a new location. These baskets also hold aquatic compost. This substrate helps your plant grow, establish, and then thrive. These baskets have lattice sides that allow water, oxygen, and other gasses to move freely while keeping the plants from spreading.
Medium to heavy loam will work as a suitable compost for pond plants. You can also purchase compost designed for aquatic use. This type of compost will contain slow-release fertilizer, meaning the nutritional goodness won’t float away when it comes into contact with the water. This fertilizer provides pond plants with necessary nutrients without creating blanket weed growth.
You can purchase aquatic plants online and at some gardening centers.
Step 3: Stabilize & Position the Plant
Place stones or pebbles in the base of containers. This weight will help anchor the plant and prevent the container from tipping over in the water.
Place the plant in the container and surround it with compost. Dress the top with a layer of gravel to protect the roots from nibbling fish while the plant establishes.
Position the potted plant in the water following specific depth recommendations provided. If you are planting a submerged plant, make sure that water covers the entire plant.
Best Oxygenating Plants for Large Ponds
Trying to populate a large pond? Fortunately, you have many options when selecting oxygenators to plant. Here are a few favorites:
Eelgrass is one of the best submerged oxygenating plants. A hardy plant, eelgrass resists nibbles from larger fish. Domesticated eelgrass produces two-foot tall wavy leaves.
If your eelgrass grows into an underwater meadow, you can easily remove the excess plant with a rake. You might also see it referred to as Vallisneria or tape grass. Eelgrass will spread quickly, so plant it in a pot in water 10 inches to six feet deep.
Fanwort is a fully submerged plant that provides ponds with ample oxygen and habitat. It grows best in water depths of three to ten feet and likes to root in muddy soil.
For a short period, fanwort can produce small flowers which float on the water’s surface.
Water Wisteria (Hygrophila difformis)
Water wisteria is an easy-to-grow oxygenator best suited to ponds located in temperate regions. In the right conditions, water wisteria can grow several inches per week.
Typically its maximum size measures just under two feet tall by one foot wide. Although its lacey leaves look delicate, water wisteria is pretty tough and will spread if not trimmed or contained in a pot.
Best Oxygenating Plants for Small Ponds
Selecting oxygenating plants for small ponds requires a little more consideration. Pay attention to available water depth and surface area. Many water plants can spread prolifically (see: algae). If you have limited pond space, choose a plant whose growth you can easily contain.
Here are three oxygenating plants well-suited for small ponds:
Arrowhead (Sagittaria subulata)
Arrowhead, also known as dwarf arrowhead or dwarf Sagittaria, is an easy-to-care-for plant best for shallow water (no more than two feet deep).
The leaves of this plant are shaped like arrowheads and grow in a thick clump similar to crabgrass. Its abundant leaves make it a reliable oxygen provider. Arrowhead will do well anywhere with temperatures 59-84F and doesn’t mind temperature fluctuations.
Hornwort (Ceratophyllum demersum)
Hornwort is a hardy submerged plant that can grow up to two feet tall. Despite its delicate appearance, hornwort requires little specialized attention. It tolerates fluctuations in temperature and light availability.
Plus, fish tend to leave it alone. Hornwort thrives in water with a pH level between 6 and 7.5. You can use small weights to anchor it or let it grow as a free-floater. Best of all, its fluffy leaf structure produces high amounts of oxygen.
Mermaid Plant (Proserpinaca Palustris)
Mermaid Plant dwells in shallow waters near the edges of a pond. It has fern-like leaves that can thrive above and below the water’s surface. These leaves provide excellent protection, allowing young fish to hide from airborne predators.
Mermaid plant grows relatively slowly, reducing the hassle of frequent maintenance. It requires full sun or partial shade and will grow in warmer water up to eight inches deep.
Want to oxygenate a small wildlife pond? Just because your pond is small doesn’t mean it can’t support a thriving ecosystem.
So long as an oxygenating plant is suited to the growing conditions of your pond (aka its water depth and light availability), the plant will benefit small wildlife ponds by adding oxygen to the water and providing habitats for small aquatic insects and animals. (Tadpoles will especially benefit from the shelter of these plants.)
Tips for Oxygenating Plants
Ready to start planting? Follow these tips before getting your hands wet:
- Don’t overpopulate. Plant three plants per square meter of water surface. Allow plants to establish before planting more. Keep in mind that many pond plants spread quickly, and it is possible to have too many oxygenating plants in a pond.
- Think variety. If you have space, planting more than one variety of oxygenating plants will increase your pond’s biodiversity.
- Check water quality before planting new plants. Ideally, you’re looking for clear water that is well-balanced and free from algae.
- Plant in season. Like land-based plants, pond plants grow during specific seasons. Plant most pond plants during the spring and summer.
Remember, although these plants produce oxygen during light hours, they will actually consume oxygen when it’s dark out (during the process of respiration).
This oxygen consumption likely won’t affect the small fish in your pond. However, if you have large fish, monitor your pond’s oxygen levels. An electric pond aerator can supplement oxygen levels during dark hours if necessary.