How to Get Rid of Green Spot Algae (GSA)

What is Green Spot Algae?

Green spot algae, or GSA, is a common problem that many aquarium enthusiasts face. It is a type of algae that can grow on aquarium glass, decorations and slow-growing plants.  In this article, we will discuss what causes green spot algae, how to get rid of it, how to prevent it and what eats it.

What Causes Green Spot Algae?

Green spot algae is primarily caused by:

  • Low phosphate and/or
  • Low CO2 levels

It is important to note that most aquasoils will absorb very large amounts of phosphate. This often leads to GSA algae on slow-growing plants such as Bucephalandra and Anubias. This is common in the early stages of an aquascape where aquasoil is most capable of absorbing phosphate. Overtime, phosphate absorbtion slows.

Green Spot Algae on Anubias

How To Get Rid of Green Spot Algae?

There are several ways to get rid of green spot algae in your aquarium:

  • Use a razor blade for the glass
  • Use a wire brush for hardscape
  • Spot dose AquaLabs Algae Aid

How to Prevent Green Spot Algae?

Preventing green spot algae can be done by taking a few simple steps:

  • Increase the level of CO2 in the water. If you are injecting Co2 in your aquarium you should be aiming for a 1.0 pH drop by the time the lights have turned on. Alternatively, ensure your drop checker is green/yellow by the time your lights have turned on.
  • Use a fertiliser with a high phosphate content. All AquaLabs Fertilisers have adequate phosphate to limit the growth of GSA
  • Remove any old or damaged leaves that are impacted by the algae.

What Eats Green Spot Algae?

  • Bristlenose will eat green dust algae but not green spot algae 
  • Otocinclus will eat green dust algae but not green spot algae 
  • Siamese algae eaters will not eat green spot algae
  • Shrimp will not eat green spot algae
  • Snails are excellent cleaners of green spot algae. This includes nerite snails, ramshorn snails and other pest or pond snails. Once the root cause of the green spot algae is addressed, snails will slowly eat it.


Back to blog