Green spot algae in your aquarium? This step-by-step guide will help you get rid of them

Author

Gilles

Published

May 01, 2020

groene puntalg aquarium

Algae in your aquarium can be a real pain. Some types, like thread algae, are super common, while others, like green spot algae, show up less often but are just as annoying. In fact, if you’ve ever dealt with green spot algae in an aquarium, you’ll know it’s incredibly stubborn, especially when it clings to your aquarium glass!

This guide makes green spot algae removal from your aquarium a breeze. What will you learn in this article?

What are green spot algae & what do they look like?

Green spot algae are a type of green algae. They appear as small green spots about 3 to 5 mm wide. These little green spot algae love older plant leaves and your aquarium glass. Because they are closely related to regular aquarium plants, green spot algae removal is not easy without hurting your plants. That’s why you’ll need this step-by-step guide!

green spot algae aquarium
This snail enjoys munching on green spot algae. Source: Fisharoma

Two types of green spot algae: hard & soft

Believe it or not, there are two types of these pesky green spots: hard green spot algae and soft green spot algae. And to make it even trickier, they look exactly the same! So how do you tell which one you’re dealing with? By touching them! Here are the main differences:

Soft green spot algae: Easy to remove. This type is often called “Green Dust Algae” (GDA) because it looks like dust in your tank. It’s most often found on plant leaves.

Hard green spot algae: Tough to get rid of. Get ready to scrub like crazy! Hard green spot algae, or “Green Spot Algae” (GSA), are those stubborn algae that stick firmly to your tank walls.

The good news? My guide for green spot algae removal works for both types. But first, let’s figure out the green spot algae causes…

 

A good plant fertilizer contributes to green spot algae treatment

 

What are green spot algae causes in the aquarium?

Green spot algae usually point to a nutrient deficiency. Here are the main causes:

Often, it’s a mix of these three issues. If you combine low phosphate levels and CO2 shortages with poor water flow—so the few nutrients can’t even reach your plants—it’s a recipe for trouble. Or in this case, green spot algae in your aquarium.

Good water circulation helps prevent green spot algae aquarium
Good water circulation helps prevent green spot algae. Source: Aqua Essentials

How to prevent green spot algae in your aquarium?

Prevention is key with green spot algae. You can avoid them by being proactive:

  1. Check your water flow and add nutrients. Follow the Estimative Index and slightly overdose to avoid deficiencies. Want a hassle-free solution? Go for my All-in-One fertilizer. Just add it weekly, and your plants get all the nutrients they need! For better water circulation, I recommend using a filter that cycles 5–10 times your tank’s volume per hour.
  2. Carefully increase CO2 levels in your tank. This is crucial but tricky—too much CO2 can harm your fish, while too little leads to algae because your plants won’t grow well. Proceed cautiously here.
CO2 set aquarium
A good CO2 system for your aquarium can be a real game-changer.

No CO2 system? Dim your tank’s lighting using floating plants or a dimmer. Less light slows plant growth, reducing CO2 demand and minimizing algae growth.

Note: Investing in a CO2 system is the best upgrade for a planted tank, especially for high-light or specialized plants. Check out my guide on buying a CO2 system.

Ready to get started? Let’s dive into the green spot algae removal process!

How to remove green spot algae from your aquarium?

Green spot algae removal isn’t fun, but staring at a tank full of green spots isn’t great either. So roll up your sleeves and get to work:

  1. Wet some filter wool in aquarium water.
  2. Scrub the glass of your tank with it. Be patient; this takes time.
  3. Test with a clean piece of filter wool. The surface should feel smooth and easy to glide over.
  4. Use an old toothbrush for tight corners or decorations.
  5. Trim plants if needed and remove algae-covered leaves.
  6. Do a thorough water change to wash away all traces of algae.

Yes, it’s a tedious task, but it’s worth it. You’ll end up with a sparkling clean tank, fresh minerals in the water, and fast-growing plants. For extra help, add fish that eat green spot algae!

Toothbrush being used for green spot algae removal
A toothbrush is a handy tool for green spot algae removal. Source: Pinterest

Fish that eat green spot algae

Fish that eat green spot algae are awesome—they bring life to your tank and help keep it clean. Here are two great options:

Siamese algae eater (Crossocheilus oblongus)

This hardworking fish loves algae. Keep in mind that they do best in groups, so get about five of them. Make sure they’re compatible with your current fish!

Neritina sp. Zebra snails

These stunning golden snails with black stripes are quick (for snails!) and love green spot algae. Honestly, they’re worth having even if you don’t have algae—they’re just so pretty. Plus, they’re excellent at preventing green spot algae from coming back.

Neritina Zebra snail, a beautiful alternative to fish that eat green spot algae
This beautiful snail is excellent for green spot algae removal! Source: ePond

Conclusion

Green spot algae treatment is all about being systematic. Ideally, you’d prevent it by maintaining good water flow, providing enough phosphate, and ensuring proper CO2 levels. Add snails or fish that eat green spot algae, and you should no longer see green algae spots on your aquarium glass.

Don’t get discouraged! If it’s not working, feel free to ask me for advice. I’m happy to help!

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