How to Control String Algae

Have you ever seen green gunk floating at the top of your waterfalls or clinging to your rocks? That’s probably string algae, an organism that commonly hangs out in ponds, feeding off excess nutrients in the water.

String algae is a natural, normalexpected and beneficial part of a balanced ecosystem – but sometimes, the stuff can go crazy and overwhelm your pond.

Here’s what we recommend doing if that happens to you:

Add More Plants

The easiest way to kill and prevent string algae is to remove its food source: nitrates. These nitrates are a naturally occurring byproduct of your pond’s nitrogen cycle.

String algae is an opportunistic feeder that will eat just about any kind of nitrate in the pond. The best way to get rid of these nitrates is being adding plants: lots of them.

Like string algae, pond plants love to consume nitrates in your water. Each color, shape and size of plant you add will consume a different kind of nitrate, so add a variety for the best nutrient uptake.

Adding plants should be your first line of defense in any string algae battle. Even though the results won’t necessarily be quick, plants will give you the best long-term protection.

Use Products

If you want immediate results in your string algae fight, you can find lots of products to help. Some popular options include

  • Aquascape EcoBlast or S.A.B.: You can sprinkle both of these products directly on to the string algae. Just make sure you remove any dead algae as it releases from the rocks; otherwise it will sink into the pond and become food for new algae.
  • Barley Straw Extract: Some people find that barley straw extract is helpful for preventing new algae growth.
  • IonGens: An IonGen is a device you install in your pond. It releases metal ions into the water through a probe, creating conditions that string algae don’t like.
  • Liquid Algaecide: Liquid algaecide will kill string algae, but it can also hurt fish if not applied properly.

If you opt to use any of the products above, you should still consider adding more plants to your pond. Doing so will limit the string algae’s food source and help prevent new growth.

Manual Removal

If you’re not too squeamish, you can always remove string algae by hand. Again, you should follow up removal with more plants to prevent new algae from growing.