How To Get Rid of String Algae in Your Pond (For Good!)

String 3

Use this article as a guide to remove string algae from your pond, by using natural solutions, and without chemicals like harsh algaecides. Pond algae control methods will vary based on the type of algae in your pond; to completely remove string algae you WILL be getting your hands dirty!


How to Control Pond Algae Naturally

While this article specifically mentions string algae removal methods, it is also very relevant for all types of pond algae control. Algae is essential to a healthy pond and this guide will teach you natural methods for keeping your pond balanced.

Too much algae can impair the aesthetics of your backyard pond, deplete oxygen, and potentially harm your aquatic life. Discoloration of water may mean that the water quality of the pond is poor, but green water does not always mean unhealthy. Always test water parameters to see how far the water has cycled and choose the appropriate solution.

What is String Algae and is it Dangerous?

String algae is a filamentous species that attaches to plants, hangs from rocks in waterfalls, or hangs on the surface of the water (which is referred to as Blanket Algae). The long strands tangle together and form thick mats that can double their weight within 24 hours!

This unsightly green mess tends to adhere directly to rocks and is not to be confused with the good algae which forms on the side of the pond and is soft, velvety, and jelly-like. Though it may appear ugly, string algae is not a major danger to your fish’s health but it can be to the overall appearance/water clarity of your pond.

To stop string algae: You must reduce the nutrients that fuel the algae growth cycle.

Excessive string algae will reduce oxygen content, but doesn’t necessarily mean bad water. Believe it or not, it is a sign of beneficial water qualities. Anything over 3″ is considered bad algae, but under that length is acceptable since it contains a beneficial variety of carpet algae which is home to important macro organisms that fully promote a healthy water column.

On the other – more dangerous hand, read our article on warning signs for blue green algae in your pond.

Nualgi Natural Pond Cleaner

Going natural is the easiest way to care for your pond over the long-term. You simply have to do less work. You get the beautiful tranquil pond you dreamed about, just without the endless pond maintenance.

Man-made chemicals & UV sterilizers create a dependency that actually weakens your pond biology & prevents natural water chemistry from balancing. Consistent use of Nualgi Natural Pond Cleaner can decrease or eliminate the use of harmful pond chemicals.

How to Remove String Algae From Your Pond

To remove and reduce string algae you must scoop it out first and then get to the bottom of the issue in your water chemistry if it comes back. String algae removal typically takes 20-70 days when using Nualgi Ponds in combination with beneficial bacteria to speed up the process. We’ve noticed results within 8 days & in extreme cases up to 4 months!

Don’t underestimate the value of physical algae removal.

A pond with lots of healthy plants will help reduce algae buildup

string algae in pond

Your waterfall will be the most difficult place to remove algae in your pond. Since the water rushes by so quickly it is difficult for water treatments to do their job effectively. To completely rid your waterfall of string algae it may take up to 2 seasons, so be patient and make sure you are not adding excess nutrients to fuel more algae growth!

Read more about the value of choosing the right aerator for your pond.

Speed up the process with Nualgi.

“The natural treatment is working so well that I haven’t had to rake and pull out buckets full of string algae like I did last year.” – See Barbara Jo’s Pond

5 Steps for String Algae Removal & Reduction

This is your best method for removing string algae. Though it may seem dirty, it is essential to do before treating so you can reduce the amount of decay. Pull the biggest bits of near the base, pull hard, and put it into a bucket. It can sometimes be difficult to pull out a lot at one time since it is soft and malleable. Physical removal is the fastest way to get algae out of your pond and take the next step to crystal clear pond water. Winding around fingers/hands is the best approach aside from a toilet or long lint brush to roll it up with. The hand approach is easier because the thin strands are difficult to clean away from brush bristles. Wearing gloves are not required but may keep you cleaner. Use a long handled brush to pull out the algae at depth.

Once you’ve removed as much string algae as physically possible, it’s time for Nualgi Natural Pond Cleaner and Beneficial Bacteria to jump into action. Rather than dosing your pond with harmful algaecides that can be detrimental to your fish and overall pond ecosystem Nualgi Natural Pond Cleaner + Beneficial Bacteria work together to recalibrate your pond chemistry. With a small regular dose of both, you give nature the helping hand she needs to rebalance your pond’s ecosystem. It’s important to be patient at this point, some users report seeing results within 8 days but it will take time. With that patience also comes to knowledge that you’re protecting your pond inhabitants and saving money on expensive UV Filters and harmful algaecides.

Place quick growing and reproducing plants in your pond to increase oxygen content. Make sure you take out the decaying plants first, as they will not help your fight against algae. Choose plants that will grow larger, consume a lot of nutrients, and will not require a lot of upkeep.

We recommend Water Lettuce, Irises, and Cattails for the spring and summer. Marsh Marigold is one of the earliest plants to sprout in the season and helps to prepare your pond for the spring. A great winter plant is Water Hawthorne which does best in cold months and has the best prices during the summer.

Make sure you remove some of your extra plants from time to time to let new growth occur in your pond.

You can solve many problems as a pond owner by placing plants to out-compete algae and suspend algae for excess nutrients. Just be careful to not add in any plants that already have algae attached!

Look for potential causes of string algae by testing your water quality. If algae is growing at a problematic level than it is time to look beyond the algae and mat and deeper into the pond chemistry. High pH and Phosphorous levels are the leading cause of algae blooms.

Examples of what can cause high pH are the clearing of algae blooms, excessive plant growth, overstocking of fish, and the introduction of foreign materials (untreated concrete, rocks containing limestone or calcium/granite). The most common cause of high phosphorous is from fertilizers that have leaked into the pond water. Iron is also a major contributor as well as grass clippings that find their way into the pond after mowing the lawn. Scoop green grass blades out immediately.

One of the most common errors by fish pond owners is to overfeed their fish, thus adding excess nutrient to the water. If there is any food left in the pond uneaten, you’ve fed your fish too much. By feeding less you also increase the fishes’ appetite for other substances in the pond. Like algae! Try feeding your fish less this summer and see how fast they will cut through a string algae mess.

A few corbicula clams in the pond is an excellent way to keep excess nutrients cleaned up and in check. Each clam filters up to a liter and a half of water per hour. Read other Koi Pond Care Tips for the Summer.

String algae can be a nuisance but with patience, a good rake, and Nualgi Ponds you can conquer this ugly mess!


The natural way to reduce fish waste, toxins & odor. Our specially formulated beneficial bacteria help naturally reduce ammonia, nitrate and phosphate levels, as well as break down fish waste. 

Nualgi Beneficial Bacteria works brilliantly well on its own. Combine it with Nualgi Natural Pond Cleaner and you unleash the power of nature to fully and completely recalibrate your pond chemistry!

Can I Use An Algaecide to Control Pond Algae?

The most common algae control method is to add a copper based algaecide to kill visible algae. Though an algaecide may be useful from time to time, you need to apply with care. If you overuse and/or kill algae off too quickly, it can come with its own set of problems from oxygen depletion, including toxic reactions for fish, native plants, and wildlife.

Many algaecides also negatively affect the “good” bacteria designed to help keep a pond cleaner. Once these are wiped out, algae can grow more readily and may force a pond owner into a never-ending cycle of chemical use. Algaecides can be effective at controlling what you can see, but this does not address the bigger problem.

Killing the algae can also contribute to more and more excess organic matter when it dies. As a result, the algae problem will come back time and again. Use Nualgi Ponds as a natural algaecide alternative and your fish will thank you with more color, activity, and happiness.

Can I Use a UV Light to Combat String Algae?

UV lights do not kill string algae. String algae is attached to different parts of your pond and therefore will not flow past the UV light. Nualgi Ponds eliminates the need for a UV light and we do not recommend using a UV light while using Nualgi Ponds.

Should I use Barley Straw & How Much?

Barley straw is a great organic product to use, but it doesn’t exactly kill existing algae and instead creates conditions that prevent the new growth of algae. Put it in your pond early as it can potentially create a temporary algae bloom later in the season. Be careful, overdosing the pond with barley straw may cause fish kills, due to the straw de-oxygenating the water as it decays.

“Since Nualgi Natural Pond Cleaner promotes dissolved oxygen it will increase the effect of barley straw and should be used together to create a strong alliance for a healthy pond environment.” Christian Shostle

2 lbs per 1000 gal of water is the recommended amount to use. In still and small pond waters the dosage of straw should be 50 grams (approximately 2oz.) per square meter of water surface area. When it is applied to cold water (less than 50°F), it may take six to eight weeks for the straw to begin producing the active chemicals that reduce algae. In warmer water above 70F, it becomes effective in as little as two weeks. In any case, barley straw remains effective for approximately six months after it is applied. If the straw starts to smell, it should be removed and replaced. It is an indication that there was too much straw for too little water.

Final Thoughts – Enlisting Help to Scoop & Remove Pond Algae

If the thought of physically scooping out algae yourself is revolting, than it is time to get creative. Might we suggest you create a story for your children/grand children about the importance of pond algae control. Or maybe you can enlist help from a neighbor who will scoop the scum. Remember to explain safety precautions around the pond and good luck!

No matter what you choose to do about the algae in your pond we are happy to help. Please try Nualgi Ponds to balance your pond and greatly reduce algae build up. If you are still having trouble, please submit a request to our pond diagnosis and troubleshooting form so we can get to the bottom of your issue.

Bottom line: Remove string algae manually, do not add unnecessary nutrients to pond water, and keep a close look on the water quality parameters. If the problematic algae continues to return it is a cause of a greater issue within your water and should be investigated further after you have removed the string algae. Patience is a virtue and it is in your best interest to take a deep breath, add some plants, and a natural water treatment.

A Natural Solution for Pond Algae Control.

Safe for Fish, Plants, Amphibians, Birds & Pets!

Nualgi’s patented water treatment + super-strength bacteria in Beneficial Bacteria work together to recalibrate your pond chemistry. With a small regular dose of both, you give nature the helping hand she needs to rebalance your pond’s ecosystem.

The result? A beautiful crystal clear pond that is a haven to fish and wildlife – and a joy to sit beside.

A Few More Tips on How to Reduce and Control Algae in Your Pond

So you’ve now learned to get rid of the string algae…but the work is not done yet!

Here is an outline of what you need to do to continue to control pond algae and keep the water clear in the future while maintaining a natural environment.

Please contact us for help if the following tips + Nualgi Ponds does not fix your algae problem.

1. Remove Leftover Decomposing Algae

Breaking down some of that excess organic matter is critical to controlling algae long term. Many ponds have from 3 to 24 inches of organic matter resting on the bottom. This organic matter releases excess nutrients as it decomposes and more so if the pond has a shortage of oxygen in its deeper parts.

A more radical solution to removing the excessive organic matter is dredging or even draining the pond, cleaning out the bottom and starting over. This can definitely work, but is very expensive. Also, once you clean out the pond, the problems can start all over again unless you take a proactive approach to managing excessive organic matter.

2. Add Extra Aeration

Adding aeration and circulation in your pond is the most important thing you can do to help prevent algae long term. Aeration increases the level of dissolved oxygen in the bottom part of the pond which increases the number of aerobic bacteria. These bacteria, in turn, begin to feed on the excess organic matter and reduce the amount of nutrients released.

3. Add Beneficial Bacteria

Beneficial bacteria work at decomposing excess organic matter, sticks, leaves, decayed fish and excess nutrients. They don’t have to be combined with aeration, but adding oxygen will significantly increase both their numbers and their level of activity at the bottom of your pond where you need them most.

4. Scoop and Remove Algae with a Rake/Eradicator

Another commonly used option for algae control is manually scraping with a rake or weed eradicator. These options are not for everyone and can require considerable time and effort to be effective.

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