How to Get Rid of Brown Algae in Aquarium?

Brown algae are every fish owner’s worst nightmare.

Are you familiar with the mossy brown stuff that quickly takes over your entire fish tank?

Well, I have struggled with this dilemma for years!

Those brownish glass skeletons can be problematic for any new fish owner.

So, How to Get Rid of Brown Algae in Aquarium?

There are many ways you can successfully remove brown algae from your aquarium, but the best method is to remove the brown algae using your hand or suction physically. You need this problem in the bud as brown algae are known to spread rather quickly.

Before we learn ways to remove this, let’s begin with understanding what brow algae actually is.

Let’s Dive In!

What is Brown Algae?

Fun fact:

Brown Algae is not really algae at all!

There are actually two widespread conditions that are mixed up with the term brown algae.

The mossy brown stuff that you are worried about is caused by diatoms and is known as Diatomaceous Brown Algae.

This frequently occurs both in freshwaters as well as saltwater aquariums.

Mostly few of them just hang around in the background, and you really have no idea that they are present.

But, sometimes conditions are present that amplify their growth, and they begin to pop up in huge numbers.

This is referred to as the diatom bloom.

Brown Algae (Video)

Difference between Algae and Diatoms

Diatoms get confused with algae due to their similar nature.

Both of them live in organic waste and need sunlight to grow.

And well both can be an immense pain until removed from the fish tank.

The only difference between diatoms and algae is that diatoms need silica to prosper while diatoms do not.

Silica is a compound that is made up of oxygen as well as silicon.

Diatoms use the silica to build strong outer cell walls for themselves.

And another thing:

You can easily eradicate the true algae by reducing light or the nitrates, but that has to effect on diatoms.

So the first step of eradicating brown algae is by removing the word algae from your thinking about stuff.

Conditions Beneficial to Diatoms

Diatoms get energy from different compounds.

They do not depend exclusively on light for their energy.

Conditions that are beneficial to diatoms include:

  • Stagnant or still water
  • Light
  • Silicates
  • Nitrates
  • Mineral-rich or hard water

How to identify Brown Algae?

The easiest and most straightforward way to identify brown algae in your freshwater fish tank is by its color.

The substance is usually mustard or rusty brown color.

It dwells on all kinds of surfaces especially glass surfaces that is where they are the most easily visible.

Just, feel a piece of glass using your fingers, and it will feel a little gritty.


In most saltwater tanks, cyanobacteria can be mistaken for brown algae.

The best way to tell the cyanobacteria apart from the diatoms is how easily it comes off the surface.

Diatoms do not peel in sheets.

When you wipe or rub them, only the part that you touch comes off.

Cyanobacteria, on the other hand, is different.

It comes off in clumps or big sheets.


Peel cyanobacteria off, apart from using it as a diagnostic tool.

The pieces that break off might infect other parts of your tank.

Hence, making the situation worse than it already is.


Diatoms do not have bubbles clinging to it, cyanobacteria on the other hand do.

Root Cause of Brown Algae

The best way to eradicate brown algae from your fish tank is to understand what its root cause is.

Many things inflame the brown algae situation in your tank.

While mostly the problem resolves on its own, but there are many other factors that you should take into consideration.


An abundance of silicates in your fish that is one of the major causes of brown algae blooms in your fish tank.

Honestly, it’s like entering into a lion’s cage wearing meat pants like Lady Gaga at MTV awards.

The level of silicates in your fish tanks experiences a spike whenever you add new gravel or substrate to your aquarium.

The brown algae (diatoms) will usually just feed on the silicates and eventually die out.

Bad News:

This could take months.

Other Sources of Silicates include:

  • Live Sand
  • Live rocks
  • Marine Salt Mix
  • Tap water

You should always check the label of the marine salt that you use and consider changing it if your salt mix contains silicates.

High Phosphates Level

You cannot have a successful aquarium without phosphates in it.

Your fish and your plants all depend on phosphates for their survival.

So, you just have to learn to live with phosphates as they are an essential part of life and you do not have a choice.

High levels of phosphates in your fish tank, can cause a lot of problems.

The high level of phosphates in tank water flare up the brown algae as well as other algae.

Phosphates are produced from the breakdown of organic waste, food particles, and dead plant material.


You should test both your tank as well as the tap water to see how much phosphates are present.

The ideal phosphate level is:

  • Reef tanks- 0 to 0.03 ppm
  • Freshwater fish tank- 0.5 to 1 ppm
  • Freshwater planted- 1.5-3 ppm

High Level of Nitrates

Nitrates are part of the nitrogen cycle.

Organic matter is broken down to produce ammonia.

Ammonia then breaks down into nitrites and nitrates as the nitrogen cycle progresses.

If you do not conduct water changes, the nitrate level in your aquarium will increase.

Brown Algae feed on nitrates.

It’s more like a pro athlete feeding on steroids.

Don’t Forget:

You should always test your tank water for nitrates.

There are many aquarium test kits like the API Master Kit, which can help you easily test the water parameters of your aquarium.

The ideal level of nitrates for all aquariums is less than 20 ppm.

High levels of nitrates do not just fuel up the brown algae they also stress out your fish.

It weakens the immune system of your fishy buddies which makes them more susceptible to various diseases.

Sources of Nitrates include:

  • Fish feces
  • Fish Food
  • Plant Matter
  • Plant fertilizers
  • Tap water

Poor Lightning

Poor lighting is one of the biggest reasons behind the brown algae bloom.

This is a somewhat controversial statement, as diatoms do not exclusively depend on lighting for energy.


Unlike other algae, brown algae do thrive in dimly lit tanks as compared to their true green algae counterparts.

In a dimly lit tank, the brown algae overcrowd the green algae.

Methods to Remove Brown Algae

Understanding the root cause of the brown algae dilemma was the first step.

Now we need to consider options that would help remove this pest from your tank.

Here are some tested techniques!

How to remove Brown Algae from Substrate/Gravel?

The easiest and the quickest way to remove brown algae from your fish tank is by using a vacuum.


Just go ahead and push the tip of the vacuum down into the bottom of the substrate.

The gravel will tumble over and this way most of the brown algae will come off.

Then you can easily suck it through the hose of your vacuum.

Removing Brown Algae from Sand

Eradicating brown algae from the sand will not be that easy.

This is because the small particles of the sand get sucked up the hose of the vacuum as well.


You should start by hovering the vacuum over the surface of the sand.

This will help to remove any fish waste.

Then proceed by pinching the nose of the vacuum; by doing this, you will enable very little suction.

Break loose the brown algae by moving the sand using the hose of your vacuum.

Then go ahead and lift the vacuum, unpinch it and remove any brown algae fro the cloud that merges.

Do this again and again until you are satisfied that the sand is all cleaned up.

How to Remove Brown Algae from Aquarium Glass?

You will need a scrubbing pad for this.


Avoid any soaps or cleansers.

All you need is a plain old scrubbing pad and a bucket of water, which will do the trick.

Place the scrubbing pad on the tank glass, just above the gravel.

Then slowly and steadily move your hand straight up the waterline.

Take the scrubbing pad out and squeeze it out into the bucket.

Do this again and again until all the aquarium glass has been cleared.

By making the upward motion you take the brown algae out of the tank, but if you move the scrubbing pad downwards, you will help break loose the brown algae into the fish tank.

The brown algae will then move around in the tank and take upstart to grow somewhere else.

Conduct Water Changes

Water changes are like the solution to most aquarium problems.

This is again true in case of removing brown algae.

When you carry out water changes, it helps to remove the high levels of phosphates as well as nitrates from the fish tank.

As previously discussed, brown algae feed on nitrates and phosphates.

In addition to that:

You should vacuum the gravel to remove fish waste.

This is because fish waste breaks down and produces nitrates and phosphates.

How to Eradicate Brown Algae from Aquarium Décor?


Remove the aquarium décor or any fake plants from your fish tank.

This ensures that when you scrape off the brown algae, it does not float around in your fish tank.

Use a soft-bristled brush to clean off the décor, or better yet a toothbrush would do.

You might even have to pull out the bleach.

Bleach helps to clean décor that have hard to clean spots or with decorations where you might end up scrapping of the paint as well.

How to Use Bleach to Clean Fish Tank Décor?

Things needed:

  • Dechlorinater
  • Buckets
  • Bleach
  • Measuring Cup
  • Tap Water

What to do?

  1. Add 1 part bleach to 20 parts of tap water.
  2. Soak the décor in the water for about 15 minutes.
  3. Empty the bleach water bucket and then rinse off the décor until you get rid f the black smell.
  4. Fill another bucket with tap water and add five times the usual tank dosage of dechlorinater.
  5. Then soak the décor in the bleach water for about 15 minutes.

Improve the Lightening

As I mentioned before, brown algae thrive in dim light.

Improving the lightening of your fish tank will ensure the growth of green algae which will take over the food source of the brown algae.

Green algae are much easier to get rid of as compared to brown algae.

So having green algae instead of brown algae can things much easier for you.


Brown Algae do not have many predators.

On the other hand, many critters will happily devour green algae.

Significant lightening can also help the plants to prosper, and you can take over the nutrient supply for the brown algae.

Add Brown Algae Eaters

Some water species happily gobble up brown algae.

Here is a list of some freshwater as well as saltwater critters that you can add to your tank.

Amano Shrimp

These shrimps do not just eat brown algae but are also fans of any other kind of algae in your fish tank.


These shrimps will not help clean your tank’s glass.

Mexican Turbo Snails

If you have watched the movie Turbo, then I am sure you know about these snails.

These snails are very efficient at eating brown algae from tank walls, gravel as well as rocks.


These snails are slightly large and will not fare well in small setups.

Nerite Snails:

These critters do not breed in freshwater; hence you do not have to worry about them multiplying.

They will help you battle the brown algae problem.

These snails also do not have a liking for plants, so your live plants will be safe.

Trochus Snails

These snails are incredible in getting rid of brown algae from all the tank surfaces.

In addition to that:

These snails can easily flip themselves over, unlike other snail species.

How to Prevent Brown Algae from Coming Back?

Stay Away from Silicates

As discussed before, silicates are the primary cause of brown algae flare up.

You can eradicate silicates from your tank in many ways.

The best thing to do is to use substrates that gather silicates in your fish tank.

And another thing:

Silicate is also present in many marine salts, so pick a brand that does not have any silicates added in it.

Fish such as livebearers and certain African cichlid do need some salt in the water at all times.

Better to use pool salt or aquarium salt, as they do not have silicates.

Increase Filtration

Brown algae thrive on organic waste after it has been broken down.


Increasing filtration is the best way to keep the brown algae away.

You need to make sure that the filter you use is compatible with the size of your aquarium.

This will help the water to be filtered efficiently and will keep the water in your aquarium on the move.

If your current filter is not giving you’re the results you desire, then go ahead and add a sponge filter.

Sponge filters are rather easy to set up, not that pricey and add a lot of biofiltration

Increase Flow of Water

Brown algae do not fare well in high water flow.

As mentioned before, it loves stagnant water.

When you increase the flow of water in your aquarium, the brown algae are unable to anchor onto the surfaces and grow.


Make sure that there are no dead zones in your aquarium.

An increase in water low will provide you with the results you are so desperately looking for.

Conduct Regular Water Changes

Maintaining your aquarium is important when it comes to brown algae. Conducting regular water changes will ensure that compounds such as nitrates as well as phosphates do not get a chance to thrive in your fish tank.

This will ensure that the brown algae have no food source to feed on, hence eliminating any traces of them.

You should conduct 25 to 50 percent water changes every week.

Do Not Overfeed

Overfeeding is another issue that goes hand in hand with the increase of brown algae in your fish tank.

You should only provide your fish with food that they can eat under 5 minutes, as extra food will just add to organic waste.

The more waste there is the more chances of emergence of phosphates and nitrates in your tank.

So do not overfeed!

Other Solutions

If none of the above solutions help you, then you can fix your brown algae problem using the following products.

Seachem Phosguard

This amazing product can help you get rid of phosphates and silicates from your fish tank using granular ferric oxide and aluminum oxide.

Two Little Fishies ATLPBR150 GFO PhosBan Reactor 150

You can use this reactor to pump water into a chamber with filter media that traps silicates as well as phosphates.

Related Questions

Does Brown Algae harm fish? No! Brown algae are harmless for fish, and it won’t kill them. Brown Algae releases oxygen which might be beneficial for your fishy friends.

How long should I cycle my fish tank? The cycling process takes about six to eight weeks.

Related Articles:

Other Sources:

Leave a Comment