How to Deal with Diatoms in a New Tank (Beginner Guide)

Embarking on your aquascaping journey is exciting, but many beginners encounter an unwelcome guest: diatoms. These brown algae can quickly coat your substrate, rocks, and tank walls, making even the most beautiful layouts look dull. If you’re seeing brown dust everywhere in your new aquarium, don’t worry—you’re not alone, and this guide will show you exactly how to handle diatoms in a new tank.

What Are Diatoms?

Diatoms are a type of unicellular algae that often appear as a brown, dusty film. They thrive in newly established aquariums, especially those that are still cycling and have unstable water parameters. Unlike green algae, diatoms are brown in color and are typically soft and easy to wipe away.

Why Do Diatoms Appear in a New Tank?

Diatoms love an aquarium environment that is rich in silicates and nitrates, both of which are abundant during the early stages of the nitrogen cycle. Some common reasons diatoms bloom in a new aquascape include:

• High levels of silicates from tap water, substrate, or decorations
• Excess nutrients (nitrates and phosphates)
• Low light levels
• Unestablished beneficial bacteria

How to Identify Diatoms

Identifying diatoms is easy. Look for:

• Brown, dusty, or powdery coating on glass, substrate, plants, and decorations
• Soft and easily wiped away with your finger or a sponge
• Appearing within the first few weeks of tank setup

If you’re still unsure, check our aquarium algae identification guide for more details.

Step-by-Step: How to Get Rid of Diatoms in a New Aquascape

1. Manual Removal

   Use a soft aquarium sponge or magnetic algae scraper to gently wipe diatoms from the tank glass and hardscape. Siphon any loose debris out during water changes.

2. Improve Water Quality

   Test your water parameters regularly. Perform frequent, small water changes (20-30% weekly) using RO/DI or filtered water to reduce silicates and excess nutrients.

3. Boost Filtration and Flow

   Ensure your filter is operating efficiently and providing sufficient flow. Good water movement discourages diatom buildup and helps distribute nutrients for your plants.

4. Add Live Plants

   Healthy, fast-growing aquarium plants (like Java fern or Anubias) will outcompete diatoms for nutrients and stabilize the tank faster.

5. Introduce Diatom-Eating Cleaners

   Consider adding Otocinclus catfish, Amano shrimp, or Nerite snails. These peaceful cleaners love grazing on diatoms and will help keep your aquascape sparkling.

6. Patience is Key!

   Diatoms are a natural part of aquarium cycling and usually disappear as your aquascape matures—typically within 1 to 3 months.

Preventing Diatoms in a New Tank

While you can’t always avoid diatoms, you can minimize their impact with these proactive aquascaping tips:

• Use purified or RO/DI water to limit silicate introduction
• Rinse new substrate and decor thoroughly before adding them
• Cycle your tank fully before adding sensitive livestock
• Limit excessive lighting during the cycling period
• Plant heavily from the start for nutrient uptake

Diatoms vs. Other Algae: When to Take Action

It’s important to distinguish diatoms from more stubborn aquarium algae like green spot or blue-green algae. Diatoms are easy to clean and short-lived in most new tanks. If you notice other algae types persisting, check out our guide on aquarium algae control for more solutions.

Frequently Asked Questions About Diatoms

Are diatoms harmful to fish or plants?

No, diatoms themselves are not dangerous to your aquatic life. In fact, many algae eaters enjoy snacking on them!

How long before diatoms go away?

Most aquascapers see diatoms disappear naturally after their tank completes cycling—usually within 1-3 months.

Can I use chemicals to remove diatoms?

Chemical treatments are not recommended. Biological maturity and good tank maintenance are the best ways to control diatoms.

Conclusion

Seeing diatoms in your new tank is perfectly normal—think of it as your aquascape’s way of settling in. Consistent maintenance, healthy planting, and some patience will ensure these brown algae fade away, revealing the beauty of your new aquascape. Want to master your first aquascaping setup? Explore our beginner tutorials for more tips and tricks!

Ready to Create Your Dream Aquascape?

If you found this guide helpful, be sure to check out our full library of aquascaping guides for beginners. Have questions or want to share your progress? Leave a comment below or join our Aquascaping Academy Community today!