3 Ways to Deal with Spring String Algae

Get Rid of String Algae in PondMore plants, more kinds of plants, more colors of plants. If you’ve ever asked us for advice on dealing with string algae, you know we usually prefer a natural solution: add more plants to the pond.

But what do you do when the plants aren't blooming for the season yet?

We receive tons of questions in the early spring and late winter about how to handle the stringy, gunky algae that sticks to rocks and waterfalls. This stuff seems to show up in force just as the weather turns nice.

During the later spring and summer, plants do a great job of keeping string algae at bay in an Ecosystem Pond. That's because irises, waterlilies, water hyacinths and the like suck nutrients out of your pond water. Each type of plant eats a different type of nutrient; a blue flower takes up a different kind than a red flower, a wide leaf uses a different kind than a thin leaf, etc. The fewer nutrients left in your pond water, the less food string algae has to eat - thus our recommendation to add more plants to your pond if you have string algae problems.

(Note that we're only talking about string algae here. This is filamentous algae you can pick up with your hand. If you water is green instead of clear, you have a different type of algae that requires different treatment. Click here if you're not sure which type of algae you have.)

You'll probably always see some amount of string algae in your pond, especially before your plants wake up for the season - and that's OK! String algae does NOT harm your fish and, if your water is otherwise clear, is actually a sign that your pond is healthy.

If you can't stand the sight of the slimy green stuff, however, we do have some tricks to help you get rid of it - even in the early spring.


At a Glance: How to Get Rid of Spring String Algae

  • Wait for your plants to come out of winter dormancy, and they'll do most of the work for you.
  • Manually remove the string algae.
  • Try a contact algae-control product.
  • Remember: It's completely normal to have some string algae in your pond, and it does not hurt your fish.

1. Wait It Out

Pond PlantsA lot of that bothersome string algae will probably disappear if you give your plants time to do their job.

As we mentioned above, string algae doesn't hurt your pond life. If you're willing to put up with the sight of it for a couple months, there's no reason to kill it or remove it from the pond.

Your plants will eventually bloom again. And when they do, they'll suck out all the nutrients that the string algae is using as food.

You can continue to control algae throughout the pond season by adding more plants to your pond. While some people especially like floating plants like water hyacinths and water lettuce for the purposes of algae control, really any plant will do the job. The trick is to make sure you have lots of plants, and a wide variety. Each one will help clear your pond of the kinds of nitrates that string algae need to survive.

2. Remove It Manually

What if you absolutely can't stand the sight of green gunk on your rocks? Or what if string algae has gone absolutely amok in your pond, distracting from the view of your beautiful fish and waterfalls?

You have options.

The easiest and most surefire way to instantly get rid of string algae is to remove it manually. Put on some gloves, grab a bucket and just pull the string algae right out of the pond with your hands.

This method comes with a few caveats.

First, make sure you fully remove any loosened algae from the pond. New algae growth will feed on dead algae in your pond if you leave any behind.

Second, don't go too crazy scrubbing your rocks. Don't scrape them completely clean, and, if you must rinse them, try to use the water from your pond. Never use cleaning chemicals. Your pond works hard to create colonies of beneficial bacteria that keep your water crystal-clear and your fish happy and healthy, and over-cleaning can wipe out these colonies. You have a little more leeway in the early spring before your bacteria have established themselves for the season - that's why we do pond clean-outs around this time of year - but a gentle approach is always best for your pond.

Finally, remember that algae will continue to grow back as long as it has nitrates to eat. The only way to remove these nitrates from your pond is to add plants.

3. Use a Contact Algae-control Product

EcoBlast String Algae ControlWe don't usually like to use algaecides, but they can help when you have a particularly stubborn algae problem.

For string algae, we recommend using a contact algaecide or algae-control product like EcoBlast or S.A.B. These products are powders that you can use to spot-treat problem areas. They break down string algae's cell walls, loosening it from your rocks so you can easily remove it with a net or from your skimmer basket.

These powders are not the same as liquid algaecide. Liquid algaecide spreads throughout your entire pond, killing algae by removing oxygen from the water. You might see the problem here: Fish need oxygen, too. If you use too much liquid algaecide - which can easily happen if you miscalculate the number of gallons of water in your pond - you risk killing your fish and other pond life.

You still need to exercise caution with powder contact algaecides, but they're generally safer because you're only adding them to the parts of your pond where you have a problem.

Always carefully follow the instructions on the container of any algae-control product. Generally, though, here's what you'll want to do:

  • Turn off your waterfalls and sprinkle a small amount of the product directly on the string algae. You want to use enough that you can see it on the algae, but not so much that the algae looks like a sugar-dipped strawberry. (Again, always follow the application instructions on the product's container).
  • If you have a lot of string algae, only treat one area at a time. Your fish have grown use to having the algae in the pond and could be overwhelmed if you take it all away at once.
  • Contact algae-control products take effect immediately. The algae will start to bubble and look bleached.
  • Wait at least 10 minutes to give the product time to work before turning your circulation system back on.
  • Use a net to skim out the algae as it breaks away from your rocks. If you have a skimmer, empty it frequently after application. Any dead algae you let decay in your pond will act as food for new algae, undoing all the work you've just done.
  • Wait a couple days to do a second application if needed.
  • Contact algaecides and algae-control products often work better in warm weather, so you might have to wait longer to see results in early spring than you would in the summer.

These kinds of products aren't a panacea for every algae problem. While you'll probably see short-term results, you're not doing anything to get rid of the source of the problem: excess nitrates in the pond. You still need to make sure you have plenty of plants in your pond to prevent future string algae growth.

If you feel like the problem is beyond what you can or want to deal with, don't hesitate to call us. We're always available to help you handle any problems that might arise with your pond. Early spring is also a great time to do a full pond clean-out, which helps your pond start the season off right. Just fill out our online form to get started.

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10 Ways to Keep Pond Water Naturally Clear

What Causes Pond Algae?

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