How to Get Rid of Brown Algae in a Fish Tank

Uh-oh! You’ve just set up your gorgeous new tank, and everything’s looking great — until you spot it: brown algae. A mysterious brown coating on the glass, rocks, or decorations. You’re probably thinking, “Is it dangerous? How do I get rid of it?” Don’t stress! 

If this is your first encounter with brown algae, you’re not alone. It’s super common, especially in new tanks. It might seem a bit intimidating at first, but here’s the good news — it’s totally treatable and manageable! 

Let’s walk you through what brown algae really is, why it shows up, and how to banish it from your tank. Ready to get your water sparkling again? Let’s dive in!

What Is Brown Algae in a Fish Tank?

Brown algae in a fish tank isn’t actually algae — it’s a type of diatom. Diatoms are microscopic organisms that form a brown, dusty or slimy coating on just about everything — glass, substrate, decorations, and even plants! 

Diatoms have silica-based shells (fancy, right?) and love to spread wherever they find the right conditions. They don’t care if you’ve got a freshwater or saltwater setup — they’ll happily move in as long as there’s a surface to cover. 

Sometimes, they might even compete with other beneficial organisms in the tank. While they don’t necessarily hurt your fish, they do make your tank look less Insta-worthy. Think of them as nature’s way of saying, “Hey, your tank’s ecosystem is still a work in progress.”

What Causes Brown Algae In a Fish Tank?

Diatoms thrive under certain conditions — whether freshwater or saltwater. Here’s what usually brings them out. 

1. Silicates Galore

Silicates are minerals that naturally exist in water — and diatoms love silicates like kids love candy. They sneak into your tank through tap water, certain substrates or even salt mixes in saltwater tanks. When they are present in high levels, they give the diatoms an all-you-can-eat feast. Yum! 

2. Too Many Nutrients

Diatoms feed off excess nutrients, mainly nitrates and phosphates. These nutrients often come from leftover fish food, fish waste, or decaying plants. If you’ve been a bit too generous with feeding or haven’t been on top of your water changes, your tank might be a nutrient buffet for brown algae. 

3. The New Tank Blues

Ah, the newbie phase or new tank syndrome! If your tank’s brand new, brown algae are basically the first guest to arrive. During this time, the nitrogen cycle is kicking in, and water chemistry is a bit all over the place. Diatoms love this phase because the water conditions are just right for them to grow. It’s just part of the process!

4. Dim Lights, Big Problem

Diatoms aren’t exactly fans of bright lights. They prefer things a little dimmer, which is why low lighting or poor or old aquarium bulbs can set the stage for their appearance. That’s their cue to take over. 

5. Wacky Water Chemistry

If your tank’s water parameters are playing seesaw, diatoms see a chance to shine (or slime). They thrive in imbalanced environments. Things like fluctuating pH, temperature, or hardness stress the tank, and diatoms take advantage of the chaos. 

How to Treat and Prevent Brown Algae in a Fish Tank

Treating brown algae in your fish tank is totally doable! Here’s how you can tackle it in freshwater and saltwater tanks.

1. Scrub Away the Brown

First things first, grab your algae scraper or a soft sponge and start scrubbing away the brown algae from your tank’s walls, decorations, and substrate. Just be gentle around your plants or corals to avoid any accidents.

2. Let There Be Light — But Not Too Much

Diatoms aren’t fans of bright lights, so take a look at your lighting setup. If it’s looking a little dim or if you’ve got old bulbs hanging around, it’s time for an upgrade. Aim for about 8 to 10 hours of light per day — enough to keep your fish and plants happy, but not enough to give algae a reason to party.

3. Get Your Water in Check

Next, let’s talk water. Brown algae love a nutrient-rich environment, so check those water parameters (nitrates, phosphates, pH). A simple water change can do wonders to lower excess nutrients and get things back on track. Fresh, clean water is the key to keeping brown algae at bay.

4. Bring in the Cleanup Crew

Why do all the work when you’ve got some hungry helpers? In freshwater tanks, snails like Nerites and Malaysian Trumpet Snails are algae-eating machines. In saltwater tanks, Trochus snails and blennies are more than happy to lend a hand. Your cleanup crew will nibble away at any leftover algae, keeping things tidy.

5. Kick Out the Silicates

If you’re getting a lot of brown algae, your tap water might be bringing in silicates, which algae just love. Consider switching to purified water (like RO/DI water) to cut down on those sneaky silicates. You can also add some silicate-absorbing filter media to your setup for extra protection.

6. Stay on Top of Maintenance

Consistency is key! Regular water changes, filter cleanings, and light checks will keep your tank in tip-top shape and prevent brown algae from crashing the party again.

FAQs

Got more questions on your mind? Let’s answer them!

Is Brown Algae Bad for Fish Tanks?

Brown algae itself isn’t dangerous for fish, but it can make your tank look a bit messy. It’s usually a sign that your tank has excess nutrients, poor lighting, or water imbalances. If left unchecked, it can smother plants and decorations, but it’s not toxic to your fish. 

Does Too Much Light Cause Brown Algae?

Actually, too little light is more likely to cause brown algae than too much. Diatoms (the little guys responsible for brown algae) prefer low light. However, prolonged periods of lighting or old, ineffective bulbs can contribute to the algae problem, so balance is key! 

Does Brown Algae Mean My Tank Is Cycled?

Not necessarily! While brown algae often shows up in new tanks, it doesn’t mean your tank is fully cycled. It’s a normal part of the “new tank syndrome” and a sign that the ecosystem is still balancing out. Keep an eye on your water parameters, and the algae should phase out as your tank matures.

What Does Brown Algae Eat?

Brown algae thrive on silicates, nitrates, phosphates, and other nutrients in your tank water. They use these as food to grow and multiply. So, if you’ve got high levels of these nutrients, brown algae will likely show up to feast!

What Eats Brown Algae in a Fish Tank?

You’ve got some hungry helpers! In freshwater tanks, snails like Nerites and Malaysian Trumpet Snails are great at munching on brown algae. In saltwater tanks, Trochus snails and blennies are your go-to algae-eating crew. They’ll keep the algae in check while your tank stays cleaner.

Banishing Brown Algae With Our FREE eBook!

So, there you have it! Tackling brown algae doesn’t have to be a daunting task. You CAN keep your tank looking sharp and algae-free. 

But if you’re still finding yourself battling cloudy water or brown algae, don’t worry! Crystal Clear Aquarium Water from KaveMan Aquatics is here to help. This guide is packed with practical tips, tricks, and easy fixes to get your water sparkling. From the simplest changes to the secret tools you might be missing — it’s got everything you need to take your tank’s clarity to the next level.

Choose between our paperback version or our FREE ebook version!