Skip to content

3 Things to Know about Pond Algae

    Whether it turns your water green or graces your rocks with a stringy fur coat, algae can prove a nuisance for your pond.Ready to wage war on this green pest? Here are three things you should know before you start stocking up on chemicals:

    String algae is a normal, expected, and beneficial part of a balanced ecosystem pond.

    At a Glance: 3 Things to Know About Pond Algae

    • A little bit of algae in your pond is normal
    • Some algae turns your water green, while other kinds cling on to your rocks or float on the surface
    • The best way to treat algae is to starve it

    1. A little bit of algae is normal

    Ponds host a complicated mix of life: bacteria, fish, plants and, yes, algae. While you can have crystal-clear water, don’t fret if you have a little bit of algae on your rocks or s slight green tint in the early spring.

    Your pond is a living ecosystem. Embrace it. Algae, in small amounts, won’t hurt your fish and can even help sustain them.

    Learn More About Your Pond Ecosystem

    2. There’s more than one kind

    The word “algae” refers to a wide range of simple organisms, but pond owners usually worry about two broad categories: single-cell algae and string algae.

    Single-cell algae turns your water green. String algae coats rocks and other surfaces, and you can pick it up with your hand. Knowing which kind you have can help you keep it under control.

    What Causes Pond Algae?

    3. The best way to control algae is to starve it

    Pond Algae

    You can find all kinds of algae treatments on our shelves, from algaecides to UV clarifiers. But at the end of the day, the best way to prevent algae is to make sure it never has enough food to get out of hand.

    Your first weapon in the fight against excess algae: beneficial bacteria. Bacteria breaks down the ammonia that builds up in your pond when fish waste and other debris start to decay. That’s a good thing – too much ammonia will kill your fish. But that ammonia turns into single-cell algae’s favorite food: nitrites.

    Luckily, cutting back nitrites is as easy as adding more bacteria into your pond. Unlike algaecides, which can kill fish if used in too-large amounts, bacteria will never harm your pond life.

    Bacteria will eat these nitrites and break them down into nitrates. String algae thrives on nitrates, but you can keep it in check by adding a wide variety of plants to your pond. Each size, color and species of plant eats a different kind of nitrate, so the wider variety of plants gracing your pond, the less string algae you’re likely to see.

    Algaecides can offer a quick fix for algae problems and can prove effective in the short-term. Bolstering your pond ecosystem with algae-starving bacteria and fish, however, will give you a safer and longer-term solution to any algae woes.

    10 Ways to Keep Pond Water Naturally Clear

    Learn more about pond algae

    Pond Ecosystems: How Skimmers, Biological Filters Keep Water Clear

    10 Ways to Keep Pond Water Clear

    Thinking About Washing Your Pond Rocks? Don’t

    The Ultimate Guide to Clear Pond Water