How to Control Green Hair Algae in a Saltwater Aquarium

Controlling Unwanted Algae Species

Freshwater aquarium in pseudo-sea style. Aquascape and aquadesign of aquarium
Andrey Nikitin / Getty Images
  • 01 of 05

    Differentiating Between Good and Bad Green Algae

    Caulerpa sertularoides

    Keoki Stender

    So, how do you know if the green algae growing in your aquarium are the good or the bad stuff? As a general rule, the good algae is intentionally added into an aquarium via planting in the gravel or attached on live rock. The bad stuff just seems to sort of "show up" when the tank conditions are right for its growth. The bad algae tend to spread and overwhelm the aquarium. Fortunately, there are methods to get rid of the bad green algae while still keeping the good green algae in your system.

  • 02 of 05

    Getting Rid of Green Hair Algae

    Cladophora vagabunda

    Keoki Stender

    A frequently asked question is: How do I get rid of green hair algae? While there are several products on the market that will reduce nitrate and phosphate levels in your aquarium water, which act as fertilizers for algae, experienced aquarists have found that preventing the causes of high nitrate and phosphate makes more sense.

    If you want to quickly drop your nitrate and phosphate (algae fertilizer) levels to something in the reasonable range (under 20 ppm nitrate, NO3, and 0.05 ppm for phosphate, PO4), the rapid nitrate reduction water change method will accomplish this in about an hour.

    For those who like to ​plan, long-term nitrate reduction or a coil denitrator might be worth looking into.

  • 03 of 05

    Is All Green Algae Bad?

    Caulerpa lentillifera

    Keoki Stender

    Not all types of green algae are detrimental to your aquarium. Many aquarists cultivate some species of the Caulerpa macroalgae in their aquarium or refugium to reduce nitrate, phosphate, and other toxins and as a food source for tangs.

    It is the nuisance type of green algae (microalgae) that can overgrow an aquarium that people find difficult to remove. Being able to identify these algae early on is very helpful in eradicating them from your tank.

  • 04 of 05

    Natural Algae Eaters

    Blue Legged Hermit Crab
    Madelyn Catob

    Some several crabs and snails consume algae. For example, the emerald crab is reputed to be an excellent algae consumer. Astrea turbo snails are a good all-around algae cleaner with large appetites. The Sailfin Blenny (Salarias fasciatus) is also known as the Lawnmower Blenny because it devours green hair algae.

    While they may do a great job of harvesting the algae for you, be very careful about adding too many of these critters to your aquarium. A common cause of death for these animals is starvation when there are not enough algae. Once they have consumed all or most of the algae, there is nothing left to sustain them, so they need to be fed with foods they can consume.

    Continue to 5 of 5 below.
  • 05 of 05

    Removing Nitrate and Phosphate From Aquarium Water


    Several products on the market will remove nitrate and phosphate from your aquarium water. Some are filter pads that absorb nitrate or phosphate that can be added into the filter chamber and periodically replaced. Several commercial solutions are available that can be added to the aquarium water to bind certain chemicals, as lowering them in the water will reduce the nutrients available for algae growth.

Article Sources
The Spruce Pets uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Mithra, R. et al. Investigation on nutrients and heavy metal removal efficacy of seaweeds, Caulerpa taxifolia and Kappaphycus alvarezii for wastewater remediation. Journal of Algal Biomass Utilization, vol. 3, no. 1, pp. 21-27, 2012.

  2. Moellin, Karin. Viruses: More Friends Than Foes. World Scientific, 2020.