How to Prevent Algae Growth in a Planted Aquarium

Algae is one of the most common problems in a planted aquarium. A little algae is normal and even healthy, but too much can make your tank look dirty, harm plants, and stress your fish. If you’re struggling with green water, brown spots, or fuzzy algae on plants, don’t worry – you’re not alone! In this guide, we’ll explain why algae grows and how to keep it under control in a simple & beginner-friendly way.

Why Does Algae Grow in a Planted Aquarium?

Before we stop algae, let’s understand why it happens in the first place. Algae loves three things:

Too Much Light – If your tank gets too much light (especially direct sunlight), algae will explode.

Too Many Nutrients – Excess fish waste, uneaten food, and fertilizers act like food for algae.

Low Water Movement – Stagnant water lets algae settle and grow faster.

1. Control Lighting 

• Use a timer – Keep your aquarium lights on for 6-8 hours max per day.

• Avoid direct sunlight – Never place your tank near a window.

• Pick the right light – Use LED aquarium lights that support plant growth but don’t encourage algae.

2. Balance Nutrients & Fertilizers 

Plants need nutrients to grow, but too much can lead to algae problems.

• Use fertilizers carefully – Add only what your plants need.

• Test your water – Check nitrate & phosphate levels every 1-2 weeks.

• Feed fish properly – Overfeeding leads to more fish waste, which fuels algae.

  
  

3. Keep Your Tank Clean 

• Do weekly water changes – Change 20-30% of the water every week.

• Vacuum the substrate – Use a gravel cleaner to remove trapped waste.

• Clean filter regularly – A dirty filter can spread algae spores instead of stopping them.

  
  

4. Add Algae-Eating Fish & Clean-Up Crew 

One of the easiest ways to control algae is by letting nature do the work!

Best Algae Eaters for Planted Tanks:

• Amano Shrimp – Eats soft algae & leftover food.

• Siamese Algae Eater – Great for hair algae.

• Otocinclus Catfish – Perfect for brown algae.

• Nerite Snails – Cleans glass & decorations.

5. Increase Water Flow 

Stagnant water makes it easy for algae to settle. Keep your tank well-circulated with:

• A good filter – Choose a filter that matches your tank size.

• A small powerhead – Helps improve water movement in bigger tanks.

• Position outlets properly – Direct water flow towards dead spots where algae builds up.

  
  

6. Introduce CO2 for Plant Growth 

Algae loves excess nutrients, but healthy plants will outcompete algae for food!

• Use CO2 injection – Helps plants grow faster & stronger.

• Try liquid carbon (like Seachem Excel) – Works as a mild algae killer.

• Maintain a good CO2-to-light balance – Too much light without CO2 can trigger algae blooms.

7. Remove Algae Manually 

Even if you do everything right, some algae will still appear. The key is removing it before it spreads!

• Use an algae scraper – Cleans glass quickly.

• Trim affected plants – Remove leaves with algae growth.

• Soak decorations in hydrogen peroxide – Helps kill stubborn algae.

  
  

Algae is a normal part of every aquarium, but with the right steps, you can keep it under control. Focus on controlling light, nutrients, and water flow, and let your plants outcompete algae naturally. Add some clean-up crew, do regular maintenance, and your planted tank will stay beautiful & healthy!