Forget About Fish: 14 Plants for Natural Pond Algae Control

Yes, fish (as well as invertebrate critters), as well as mechanical and chemical solutions, can be helpful when it comes to pond algae control. But did you know that plants are the real heroes here?

If you’re struggling with algae in your pond—or just looking for prevention options—keep reading. Some of the most invaluable potential allies in the battle against pond scum also produce beautiful flowers, enrich the micro-ecosystem around them, and help keep your water feature looking its best.

Why are plants better for pond algae control?

Most pond owners have been there: one fine sunny morning, you approach your aquatic masterpiece with a coffee in hand to check on the fish, only to find them gone. Okay, not actually gone, but invisible, trapped in a green cloud or hidden between hairy tangles. Something has disturbed the pond’s balance and algae have taken over, which can actually happen almost overnight in some cases.

What to do?! Given how easy it is for our water features to be invaded by algae, pond algae control is a pretty big industry. After discovering the green muck, most of us run out to buy chemical algicides, expensive UV sterilizing units, and an army of algae-eating fish. But as we mentioned in the intro, in many cases, plants do the job just as well—or even better.

What causes algae, really?

The thing about the three main other pond algae control options is that they don’t fix the root causes of algae blooms. There are a lot of detailed natural and chemical processes involved, but algae explosions are mostly the result of excesses:

1. Excess light: lots of sun allows algae to photosynthesize abundantly.
2. Excess nutrients: nature’s waste products (resulting from decay, animal poop, etc.), like nitrogen and phosphorus, are food for algae.
3. Excess temperature: can greatly speed up algae growth rate, and reduces dissolved oxygen levels in the water. This causes competition, such as plants, to die off… releasing further excess nutrients.
4. Stagnant water: another factor that chokes out the competition through oxygen reduction, allowing hardy algae to take over.

Why chemicals and fish don’t always work

If you get an algae bloom due to excess light and nutrients and then use an algicide, the situation might improve temporarily. But if you don’t fix those excesses, the algae can still come back—it might even do so quite quickly, as the dead algae provide a nice boost of nutrients for the next round.

Alternatively, let’s say you add a few goldfish, which are natural algae eaters. However, they also excrete wastes that algae love to feed on. Instead of fixing the four root causes of algae, adding algae eaters potentially contributes to one of them!

This isn’t to say algae eaters don’t have their place in your pond, but they’re not the ideal first line of defense.

The magic of plants

The magic of plants is in the fact that they can help correct some of the factors that cause algae, without significantly contributing to any of them.

In fact, with the exception of cause #4, stagnant water, plants have the capacity of reducing all the excesses that cause algae. Water movement is easy enough to add by increasing filtration, or with an extra powerhead or fountain/waterfall feature.

Here’s how plants help out:

• Various plants mainly grow on the surface, or overhang it. This means they shade the water, helping to reduce the light that algae depend on to grow.
• When direct sun is partially blocked, temperatures in the pond will also stay lower. This slows algae growth and prevents oxygen-starved dead zones.
• Plants use the same nutrients that algae do: natural waste components. The fact that they compete for the same nutrients can make it harder for algae to get a foothold.

Sure, plants do eventually die, which introduces nutrients into the water column as they decay. But these nutrients will have to be split between said plants’ offspring and algae, rather than contributing to algae growth alone! As you can see, plants are actually the ultimate natural form of pond algae control.

All plants will contribute to pond health and help keep algae at bay. Some are particularly effective, though, as their large leaves help provide lots of shade or they’re vigorous growers that suck up large amounts of nutrients. Below, let’s have a look at FantaSEA’s favorites!

Tip: Worried the plants will overgrow? That’s where herbivorous fish like goldfish can come in to strengthen your micro-ecosystem. They can help keep greenery under control, while at the same time producing the nutrients that keep it healthy. Balance is created, and algae happen to hate balanced ponds.

Plants for natural pond algae control

Floating plants

• Lemna minor or duckweed (cool to tropical): excellent at competing with algae but extremely vigorous. If you don’t have plant eaters like goldfish or koi, they can overgrow your pond entirely.
• Pistia stratiotes or water lettuce (subtropical to tropical): efficient and nice to look at, with feathery roots that provide shelter to small critters like baby fish. Very regular maintenance needed in warmer climates.
• Limnobium spongia or American frogbit (cool to tropical): native to parts of the US, but a banned invasive in others. Absorbs large amounts of nutrients, but check if it’s legal where you live.
• Azolla sp. (cool to tropical): native to parts of the US, invasive in some other areas due to its quick growth. With regular maintenance it will work in some ponds; thanks to its nitrogen-fixing abilities, it can be used as a natural fertilizer.

As you can see, all floating plants are rather vigorous. It’s important to check local regulations before introducing them into your pond. Some, like water lettuce, are fine in cool climates but invasive and often regulated in warm ones (like the southern US).

Some notorious floaters (aquatic ferns known as Salvinia and a pretty bloomer called Pontederia crassipes or water hyacinth, for example) are widely banned. Avoid them for the sake of the environment as well as your pond (and by extension your sanity!).

Aquatic plants

• Nymphaea or water lilies (cool to tropical): provide shade, making it harder for algae to grow. Tropical water lilies grow year-round, while hardy ones go dormant during the winter months. As long as their rhizomes don’t freeze, they return in spring to treat you to a flower fest.
• Elodea or anacharis (cool to tropical): native to the Americas and known as a vigorous oxygenator. This stem plant usually roots in the substrate but can also grow into large, free-floating mats; some species are invasive in certain regions, so check local regulations.
• Ceratophyllum demersum or hornwort (cool to tropical): also known as coontail thanks to its fluffy appearance, this stem plant is naturally found throughout almost the entire world. It excretes chemicals that inhibit the growth of floating algae and cyanobacteria (that mucky stuff known as blue-green algae), making it a great addition to your arsenal.
• Najas guadalupensis or guppy grass (subtropical to tropical): another USA native, this vigorous grower does well when left floating but can also be rooted in the substrate. Sometimes it works as an annual in cooler climates, but it’d have to manage to seed itself in order to be able to return year after year.
• Hippuris vulgaris or mare’s tail (cool to subtropical): we love the look of this plant! Although it roots in the substrate, mare’s tail stems eventually break the water surface, emerging like a mini pine forest. Can be quite a vigorous grower.

Tip: Some herbivorous fish love munching on plants (we’ve seen grass carp lifting themselves out of the water to eat grass planted around the pond’s edges!). Not ideal if you’re trying to cultivate plenty of greenery—plant cages and natural barriers can help.

Marginal plants

• Pontederia cortadata or pickerelweed (subtropical to tropical): your typical algae-choking margin plant, this vigorous grower is native to the USA. It doesn’t just help your pond thrive, but its sweet purple blooms also feed important pollinators.
• Iris versicolor or blue flag iris (cool to tropical): forget about the invasive yellow flag iris and go for a native species instead! Its gorgeous blooms and nutrient-hungry nature make the blue flag iris an excellent choice for planting around your pond
• Caltha palustris or marsh marigold (cool to subtropical): not the absolute most efficient nutrient buster, but look at those lovely yellow blooms! As an early bloomer, it’s an important food source for pollinators during the spring months.
• Juncus effusus or common rush (cool to tropical): this hardy nutrient slurper is another excellent native plant to plant around your pond in order to provide some shade and fight algae.
• Equisetum hyemale or rough horsetail (cool to tropical): our recommendation for small ponds instead of cattails, which are a little too vigorous sometimes. Although rough horsetail is not native to the USA and can be a quick grower, it doesn’t appear to have much invasive potential. Yay!

We have to note that there are so many options in terms of marginal plants that there’s no way we can list them here. Check out your favorite garden center for native rushes, sedges, cattails, and much more. They should be able to help you choose the optimal plants for your specific local climate.

Conclusion

When it comes to pond algae control, the keyword is “balance”. And although plants can’t achieve balance all on their own (you’ll also need to prevent overstocking your pond, add water movement, and perform regular maintenance), they can go a surprisingly long way! Use floaters, lilies, aquatic plants and marginal species to both beautify and de-algify your pond.

Dreaming of your own backyard pond but worried it’s too complicated or will take up too much of your time? We can help! Just contact the FantaSEA Aquariums team with your ideas and we’ll make them reality.