If you're dealing with green water, string algae, or that fuzzy mess growing all over your pond rocks, you're not alone! Pond algae is one of the most common headaches for backyard water gardeners. At WetPlants.com, we hear these questions all the time:
"Why do I have algae in my pond, and how do I get rid of it?"
The answer starts with balance. Algae thrives when there's too much sunlight, too many nutrients (like fish waste or fertilizer runoff), and not enough competition from beneficial plants. That's where the right aquatic plants come in.
Why Algae Grows in Ponds
Algae isn't always a sign of disaster. In small amounts, it's part of a healthy ecosystem. But when it takes over, it's usually because one or more of the following reasons:
- Your pond gets too much direct sunlight
- There’s an excess of nutrients, especially nitrates and phosphates
- There's a lack of oxygenating plants or nutrient-hungry plants
- Your pond is new and not established yet
- You don’t have enough shade or surface coverage (often hand-in-hand with the too much direct sunlight part)
The good news? You don’t need chemicals to get it under control. You just need the right mix of aquatic plants from WetPlants.com to outcompete the algae. As we always say, "Nature always prevails!"
Common Types of Pond Algae (And How to Spot Them)
Not all algae is the same, and identifying what you're dealing with can help you choose the right strategy. Here are the most common types of pond algae and how to recognize them:
1. Green Water (Planktonic Algae)
This is the classic "pea soup" look. Your water turns cloudy or bright green. It’s caused by microscopic algae suspended in the water column and is often triggered by too much sunlight and excess nutrients.
🟢 Look for: Water that appears murky green even if the surface looks clear.
2. String Algae (Filamentous Algae)
Also called "blanket weed," this forms long, hair-like strands that tangle on rocks, waterfall edges, and plants. It can grow rapidly in sunlit, shallow areas.
🟢 Look for: Slimy green threads stretching from surfaces or floating in mats.
3. Surface Mats (Floating Algae)
These algae form loose or dense mats on the water’s surface, often resembling green scum or foam. They can quickly cover a pond if not controlled.
🟢 Look for: Floating patches of green that can be skimmed off by hand or net.
4. Blue-Green Algae (Cyanobacteria)
Though not technically algae, these bacteria form dense, often toxic blooms. They can appear blue-green, brown, or even reddish, and may give off a musty or foul odor.
⚠️ Look for: Discolored surface film with a paint-like or oily sheen. Avoid contact, especially for pets and wildlife.
Knowing what kind of algae you have can help you pick the best plants to fight it off—and at WetPlants.com, we’ve got algae-busting options for all of the above.
How to Control Pond Algae with Plants
At WetPlants.com, we specialize in pond plants that do exactly what algae hates: block sunlight, suck up nutrients, and improve water clarity. Here are our top recommendations:
1. Hornwort (Ceratophyllum demersum) 
Hornwort is a superstar when it comes to algae control. This fast-growing oxygenator floats or can be weighted down, and it competes with algae for nutrients, especially nitrogen. It also releases allelopathic chemicals that naturally suppress algae growth. Bonus: fish love hiding in it!
➡️ Available now at WetPlants.com by the LB and in multi-stem bundles.
2. Dwarf Water Hyacinth
A floating favorite, dwarf water hyacinth has beautiful lavender blooms and dangling root systems that absorb tons of excess nutrients from the water column. They shade the surface and grow fast in warm weather, which is exactly what you want when fighting green water.
➡️ Grab yours from WetPlants.com while supplies last.
⚠️ Note: Water hyacinth is illegal in certain states including CA, FL, LA, TX, AL, and others. Check local regulations before ordering.
3. Water Lettuce (Pistia Stratioes)
If your pond gets full sun, this is another great floating option. Water lettuce provides dense surface cover and is one of the fastest ways to reduce sunlight penetration, which chokes out algae before it gets started.
➡️ Fresh water lettuce available seasonally at WetPlants.com.
➡️ Also available: Rosette Water Lettuce.
⚠️ Note: Water lettuce is restricted in CA, FL, LA, TX, and a few other states.
4. Water Lilies (Nymphaea spp.)
Hardy or tropical, water lilies are a must-have for algae control. Their big floating leaves block sunlight from reaching the pond floor, which helps prevent string algae and green water. Plus, they’re stunning when in bloom.
➡️ Explore our full water lily collection on WetPlants.com, including red, pink, white, and yellow varieties.
5. Pickerel Rush (Pontederia cordata)
A fantastic marginal plant that thrives at the pond’s edge, pickerel rush pulls nutrients directly from the soil and shallow water, helping reduce algae-forming compounds. Its tall structure also acts as a natural filter and provides great habitat for pollinators.
➡️ Available now in blue and white options at WetPlants.com.
6. Submerged Oxygenators (Hornwort, Moneywort, Vallisneria, etc.)
Adding submerged plants like Hornwort, Moneywort (Bacopa monnieri), and Vallisneria helps oxygenate the water and provide competition for algae at all levels of the pond. Moneywort in particular is great at absorbing nitrates and thrives in both shallow and deep water zones.
➡️ Check out our oxygenator plants at WetPlants.com.
7. Water Poppy (Hydrocleys nymphoides)
If you're after something a little different, water poppy is a floating-leaf plant with bright yellow blooms and strong roots that help absorb excess nutrients. It’s an underrated algae-fighting plant that we highly recommend.
➡️ Water poppy is in stock now at WetPlants.com—get it before it’s gone.
The Impact of Plant Coverage on Algae Control
Wondering how much plant coverage really matters? A lot. We've created an easy-to-follow visual to show the relationship between plant coverage and algae presence in a typical backyard pond:
As the chart shows, algae growth drops dramatically as plant coverage increases:
| Plant Coverage (%) | Relative Algae Growth (%) |
|---|---|
| 0 | 100 |
| 25 | 75 |
| 50 | 40 |
| 75 | 15 |
| 100 | 5 |
This relationship isn't just theory; it’s backed by research. A study published on PubMed Central (PMC) found that ponds with greater aquatic plant coverage had significantly reduced levels of total nitrogen and suspended solids—two of the main drivers behind algae blooms.
In other words, more plants = less algae.
If you’re struggling with murky water or string algae, aim for at least 50–70% plant coverage in your pond. Floating plants like water lettuce, hyacinth, and water lilies, combined with marginal plants and submerged oxygenators like hornwort and moneywort, can make a dramatic difference.
Putting It All Together: Building a Balanced Pond
If you're serious about long-term algae control, you'll want a mix of floating, marginal, and submerged plants. Think of it like building an underwater army:
- Floating plants (like hyacinth and water lettuce) shade and absorb nutrients
- Marginal plants (like pickerel rush) filter runoff before it hits the pond
- Oxygenators (like hornwort, moneywort, and vallisneria) clean the water from within
It’s all about plant density. The more coverage you have, especially on the surface, the less sunlight and nutrients algae has to grow.
How Long Until You See Less Algae?
If you're adding aquatic plants to fight algae, you’re probably wondering: when will I start seeing results?
In most ponds, you can expect to notice a visible improvement in 2 to 4 weeks, especially if you've added fast growers like hornwort, water hyacinth, or azolla caroliniana. These plants get to work quickly by absorbing excess nutrients and blocking sunlight—two things algae depends on.
However, results may vary depending on:
- Sun exposure: Full sun ponds may need more surface coverage for results to show.
- Bio load: Heavily stocked ponds produce more waste, which feeds algae.
- Filtration: Weak or undersized filters may slow the cleanup process.
- Runoff: Fertilizers or organics washing into your pond can keep algae fed, even with plants in place.
- Temperature: Warm water speeds up both algae and plant growth, so timing can shift with the season.
For best results, aim for a balance. Add a variety of plants, avoid overfeeding fish, and stay on top of regular maintenance. At WetPlants.com, we’re here to help you find the right mix.
Simple Pond Maintenance Tips to Prevent Algae
Even with the right plants in place, a little regular maintenance goes a long way toward keeping algae in check. The plants will do their job, but it's on you to make sure you're setting the plants up for success. Here are a few easy habits to adopt:
- Skim debris regularly: Remove fallen leaves, dead plant matter, and uneaten fish food to reduce decaying organics.
- Avoid overfeeding fish: Excess food leads to nutrient buildup, which feeds algae. Feed sparingly and consistently.
- Trim plants as needed: Cut back dying leaves and flowers to keep your plant filter system running at full strength.
- Check your filtration system: Make sure your pond pump and filter are appropriately sized and cleaned routinely.
- Do partial water changes: Replace 10–20% of the water every couple of weeks to dilute excess nutrients, especially in heavily stocked ponds.
- Control runoff: Keep lawn fertilizer, soil, or mulch from washing into your pond during rainstorms.
Good pond health is about balance. With healthy aquatic plants from WetPlants.com, plus a few routine tasks, you’ll spend less time battling algae and more time enjoying your water garden.
Tips for Success
- Cover 60–70% of your pond surface with plants
- Add a variety of species for different nutrient zones
- Avoid overfeeding your fish
- Rinse new plants before adding them to avoid introducing algae
- Remove dying leaves to prevent decay buildup
Need Help? We’ve Got You.
If you're not sure where to start, WetPlants.com has curated Algae-Fighting Plant Packs that take the guesswork out of it. Whether you're battling green water, string algae, or just want clearer pond conditions, our team is here to help.
We're not just a plant store. We're pond people too.
So next time you're staring at a murky mess, remember: the solution is often as simple as adding more plants. And at WetPlants.com, we’ve got just the ones you need.
Shop algae-fighting pond plants today at WetPlants.com and bring your water garden back to life.