How To Get Rid Of Brown Algae In Fish Tank – 4 Effective Pro Tips

Algae is a common problem in fish tanks and can be challenging to get rid of. Brown algae are one type of algae that can overgrow and become a nuisance. 

You can do several things to get rid of brown algae in your fish tank. 

In this post, I’ll take a look at some of the best methods for getting rid of brown algae. I’ll also discuss how to prevent it from coming back.

Let’s get started to know – How To Get Rid Of Brown Algae In Fish Tank!

What Is Brown Algae

Interesting fact! Brown algae aren’t actually algae at all…

Brown algae are tiny organisms almost always present in any aquatic environment. The different species can be found in both freshwater and marine.

brown algae are diatoms

They are diatoms! In fact, diatoms are so small they can only really be seen using an electron microscope! But you can see a brown layer which is actually a “diatom colony.” 

Brown algae aren’t actually algae at all… As you can see, brown algae is actually a bacterial colony. So it’s not what most people think of when they hear “alga.” 

So, if you use the same removal methods on brown as opposed to other types, it’s likely that your cleaning efforts will be frustrated by this pesky animal. 

How To Identify Brown Algae

The easiest way to identify brown algae in your freshwater tank is simply by its color. It’s usually a rusty or mustard shade and will grow on surfaces like glass (and even substrate) if left unchecked for too long!

In marine aquariums, cyanobacteria and brown algae look similar. The best way to tell the difference between diatoms and cyanobacteria is how easily you can take them off. These cyanotic organisms peel off in sheets or clumps, while the brown algae won’t.

Only the part you touch will come off if you wipe brown algae!

Find The Root Cause Of Brown Algae

Juicy, green growth is a sign of life in your tank. But if you find brown algae growing out of control, then there may be something wrong with it and needs fixing before things get worse!

Aquarists have been struggling with various problems concerning these pesky animals for years! The most efficient and fastest way to remove brown algae from your aquarium is by identifying and eliminating its root cause.

Presence Of High Nitrates

Nitrates are a natural byproduct of the nitrogen cycle in aquariums. As fish waste breaks down, it puts off ammonia which gets processed through beneficial bacteria before turning into nitrite – then eventually leading to an accumulation if not removed with regular water changes!

Brown algae in aquariums come from the love of nitrates. So, it’s no surprise that high levels are vital to their growth! The best way to keep your tank brown-algae-free? Test for nitrate levels and make sure they stay under 20 ppm at all times! Regular water changes help a lot.

Also Read: How To Lower Nitrate In Freshwater Aquarium?

Poor Lighting

It is experienced that brown algae thrive in low lighting. But, many people argue that brown algae have nothing to with light, indeed! Because the type we call “brown algae” doesn’t actually have any algae at all – they’re diatoms! 

In a tank of bright lighting, green algae outcompete their brown counterparts for nutrients in the water column. So there is an indirect relationship between aquarium lighting and brown algae growth!

Presence Of Phosphates

The phosphate level in your tank is a good indicator of the typical lifecycle in your aquarium- it’s a part of life. But accumulating phosphate can cause brown algal blooms and other bad-tempered fishkeeping problems, so regular maintenance is vital!

Regular water changes can keep phosphate levels down in your aquarium! The ideal ranges of phosphate levels are: 

 Freshwater Fish-Only Tanks – 0.5-1 ppm

 Freshwater Planted Tanks – 1.5-3 ppm

 Reef Tanks – 0-0.03 ppm  

Excess Silicates

When you add new sand substrate, especially play or blasting/pool sand, to your fish tank, it can create an abundance of silicates.

Some salt mixes contain high silicates, so when adding them to your marine tanks, make sure not too much ends up a silicate spike!

4 Effective Ways To Remove Brown Algae

Brown algae can ruin your tank. It wastes space, costs money to remove and maintain it in the long run, makes you unhappy with what’s going on inside.

But don’t worry – there are plenty of ways for us anti-algae warriors out there who want their tanks clear as crystal without harming our fish or decorating themselves from head toe (trust me).

1) Regular Water Changes

Water Changes to remove brown algae in a fish tank

Doing regular water changes is an easy way to keep your tank looking clean and fresh by eliminating brown algae. 

When you change out the old water, it removes any nitrates or phosphates that may have been consumed by brown algae. So removing nitrates and phosphates make diatoms starve, and they don’t grow back in! 

When doing this process for best results, always go down with a gravel vacuum cleaner right after vacuuming up all fish waste from underneath the substrate.

Also Read: How often to Change Water in Fish Tanks? (Get the Proper Guidelines)

2) Improved Lighting

A broad spectrum of light to remove brown algae in a fish tank

The lighting in your tank can be improved to encourage more green algae growth. This will help control brown algae because it’s easier and less messy than the brown variety. Green algae might outcompete the brown for nutrients in the water column if you have both species present together.

The best lighting for a tank is the kind that reaches down into dark depths. A broad spectrum of light will make it easier to control brown algae and encourage green, instead!

3) Brown Algae Eaters

Introducing some new friends to your tank might just be the solution you need. If brown algae are taking over, these guys will help keep it in check!

Freshwater Species That Eat Brown Algae

brown algae eaters freshwater

Nitrile Snails: Nitrile Snails are a great way to get rid of brown algae in your tank. They love to feed on brown algae. These snails cannot breed in aquariums, so you won’t have hundreds upon thousands walking around! 

Amano Shrimp: Amano shrimp are a unique kind of freshwater crustacean that will eat just about any type of algae. But they won’t clean the glass surface of your tank!

Bottom-Feeder Fish: Bottom-feeder fish like Otoclinus catfish and Bristlenose plecos are believed to prefer brown algae but will also eat other things to survive. However, these choices may not always be enough to consume brown algae – which is why I recommend trying nerites snails instead! 

Marine Species That Eat Brown Algae

brown algae eaters saltwater

Trochus Snails: The Trochus snail is a genus of marine snails that clean up diatoms on your marine tank surfaces. They’re also cool because they can right themselves if you flip them over, unlike many other species where this would be impossible!

Mexican Turbo Snails: The Mexican Turbo snail is a nocturnal creature that feeds on diatoms. So, they can be efficient at eating diatoms off the live rock and tank walls. But their large size means they don’t work well for smaller aquariums.

4) Manual Removal Of Brown Algae

The most typical way to get rid of brown algae from your tank is through manual removal using tools such as nets/nets, piles of clothes…or even old socks if need be. However, these methods may take some patience, depending on how much coverage needs to be done by hand.

Removing Brown Algae From The Glass Surface


Never fear aspiring aquarium owners! If your fish tank is glass or acrylic and you notice brown algae coating the walls of yours, then simply wipe it away with a single smooth motion.

To clean brown algae from the aquarium glass, take a scrubbing pad and put it against the surface right above where you have the substrate. Keep steady pressure on the scrubbing pad while pulling up until getting back to above the waterline.

Squeeze the scrubby in a bucket before putting it right back into the aquarium and repeat the process until all algae are cleaned from the surface.

Removing Brown Algae From The Substrate

The method you choose to remove brown algae from your aquarium substrate will depend on what type of bottom material is present in the tank. You can use pebbles, gravel, or sand, and the technique will be different for all.

Removing Brown Algae From The Substrate
Pebble/Gravel Substrate

If you have brown algae on your gravel/pebble, the best way to get rid of it is with a vacuum. Really push down hard into those rocks and watch as all those pesky diatoms are sucked away!

When it’s time to clean brown algae from the substrate, make sure you only vacuum up the top layer of gravel. This way, you can remove all those pesky diatoms (without losing beneficial bacteria) that love living on their surface and causing problems for us aquarium lovers!

Sand Substrate

The brown algae will only grow on top of your sand. It can be removed by grabbing a fish net and gently running it across the surface to remove any unwanted films, leaving behind as many substrate materials in their place!

If you want to remove brown algae from the sand by a siphon, it is a bit trickier. Sand easily gets sucked up into the siphon. 

  • Wave gravel vacuum just over the sand surface, mixing fish waste with water.
  • Stir well using handheld vacuums until all brown algae particles have been broken down into tiny bits.
  • Then get the vacuum just above the sand layer, slowly vacuum to get cloudy water sucked in.
  • Repeat the process until it is cleaned enough.

Also Read: How to Clean Aquarium Sand, the Simplest Way in 7 Steps!

Removing Brown Algae From Decors

Removing Brown Algae From Decors

Here are some tips for cleaning fake plants and decor from the tank so you can get rid of those pesky diatoms. Make sure not only do they come off as many as possible, but also without leaving any behind that could attach themselves somewhere else inside your aquarium! 

Scrubbing is always an option, too – just use a soft-bristled brush or toothbrush on these types & shapes; if scrubbing isn’t enough to remove all traces, then bleach might be needed sometimes as well, depending upon how bad things have gotten with brown algae growing everywhere.

The bleach-cleaning process is a bit tricky!

Mix 1 part bleach to 20 parts tap water. Let all decors soak for 10 minutes, then dump and rinse until you cannot smell any more chemicals! Next, fill a bucket with fresh tap water and add the appropriate amount of chlorine dissolver. Soak your decorations in it for 10 minutes to get rid of any trace amount of chlorine before putting them back in the tank!

How To Prevent Brown Algae from Coming Back

If you remove all of the brown gunk from your tank, ensure it’s kept clean by following an appropriate routine. 

Undoubtedly, you don’t want brown algae to come back in your tank! 

Luckily for us, though, there are some great tips out there that will help prevent your tank from being recolonized by these pesky diatoms!

How To Prevent Brown Algae from Coming Back

Step 1: Adequate Filtration

One of the ways to keep brown algae at bay is by increasing filtration. Because diatoms love eating organic compounds from uneaten food and fish waste. 

The right filter is key to keeping your fish tank clean and healthy. Ensure you have the right one for your tank size! 

The best option would be a canister type to purify and keep waste moving through quickly. So it doesn’t start piling up on top, leading directly back to harmful chemicals produced from organic materials like food scraps.

Step 2: Water Changes

It’s crucial to keep up with regular water changes, or brown algae will come back. When you change out the old tank water and add in new fresh stuff each week – it helps reduce nitrates and phosphates in the water.

Diatoms primarily feed on nitrates and phosphates, so reducing their food makes the tank unsuitable for them to live.

Make sure 25%-50% partial water changes weekly!

Step 3: Avoid Overfeeding

Do you see that excess food in your fish tank? It will rot and release nutrients to brown algae if not taken care of. You should only feed what they can eat within 2 minutes – otherwise, all the extra just gets accumulated as waste!

Some goldfish species are always hungry and can eat as much as you provide. But even they eat all, more food means more poops, and the result is the same – more nutrients for brown algae!

Step 4: Increase Water Flow

Brown algae or diatoms really don’t like high water flow. Instead, it prefers more stagnant tanks with low velocities, so you’ll have to add some additional powerheads to ensure your fish tank has fast-moving waters! 

If the water’s moving, diatoms have a hard time gathering and sticking onto surfaces. All that movement will ensure those pesky algae don’t grow.

Step 5: Avoid All Sources Of Silicates

Brown algae are a pesky problem, and silicates are one way to ensure it never goes away. 

Silicates can cause brown algae blooms and should be avoided. Live sand, salt mix, and silica sands may all contribute an abundance of silicates in your aquarium water, so you have to ensure not adding any by means – control brown algae overgrowths!

Tried Everything, But Brown Algae Exists In Your Tank?

The brown algae are like an unwanted guest in your pet’s house. It sneaks up and starts to take over, but now it’s time for the big guns! If you tried everything stated above but still faced the problem, there are more solutions! 

Chemical Filtration

Effective chemical filtration can eliminate nitrates, phosphates, and silica from the aquarium water, thus controlling brown algae growth! Different types of chemical filter media are readily available.

For freshwater…

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For saltwater…

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Some people use nitrate and phosphate reducer dosing chemicals to control brown algae in their water. These chemicals cut off the nutrients that give these pesky creatures food, making them unable to grow at an alarming rate!

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Protein Skimmers

Protein skimmers are for saltwater aquariums. Protein skimmers are excellent for controlling brown algae because they eliminate wastes before they get the chance to break down and produce nitrates and phosphates.

UV Sterilizer

UV sterilizers pass water through a tube with an especially bright UV or UVC light. The harmless rays of light can kill algae, diatoms, and bacteria that might be floating around in your tank!

Also Read: Best UV Sterilizer For Aquarium – Review & Buying Guide

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RO Water

Tap water can be riddled with impurities. Some of these include high nitrate and phosphate levels and added silicate materials found in most tap waters worldwide. Running an RO (RO Water) filter will help you cut down on those pesky minerals that encourage brown algae and improve the overall water quality of the fish tank!

Can Brown Algae Harm Your Fish?

For fish- only tanks – no! Brown algae may seem yucky to you, but it’s actually a good thing for your fish. The brown diatoms in this type of alga feed on carbon dioxide and release oxygen as waste! This increases dissolved oxygen levels which benefits your fish, making the healthful environment around them.

But brown algae are actually terrible for your aquarium plants and corals. The worst thing you can do is leave brown algae unattended in a reef tank or planted aquarium. It will compete with the plants/corals for nutrients and block out sunlight, resulting in their death!

Wrapping Up

Brown algae can be a nuisance in your fish tank, but it doesn’t have to stay that way.

If you’ve ever had a brown algae problem in your fish tank, then you know that it can be an annoyance and look terrible. But once it grows out of control, there are many ways to get rid of this pesky growth. 

In the article, I went over some root causes and prevention techniques for this type of thing happening again in the future. 

You might also want to ask our experts about how they prevent their tanks from getting brown algae with these tips too!

If you have any questions, please leave them below! 

Sujit Modak

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