Saltwater Algae Control: Brown Algae 15

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Brown algae can be one of the most annoying things in your aquarium as a fishkeeper. Just when you thought you cleaned your tank up squeaky clean you start seeing some brown nasty stuff filling up your tank, brown algae! You wonder where they keep coming from, but without any prior warning they pop up into your aquarium and leave you wondering how they got there.

Not only are brown algae nasty looking but they also cause a high imbalance in the saltwater aquarium’s ecosystem. If not kept in check it can completely ruin not only your pretty looking fish and reefs but also their health.

Brown algae can be quite problematic to remove, but with the right tools and knowledge it shouldn’t be quite as hard. Cleansing your system by removing brown algae would mean that the fish, plants and reefs would be much healthier and be living in an ideal ecosystem without the interference of brown algae. Your aquarium would get back its original and natural look by weeding out the ugly brown algae that has been squatting in your aquarium.

We’re going to cover in this article what brown algae is, what are the advantages and disadvantages of having them in your aquarium and how you can identify them.

We’ll also touch upon how you can prevent brown algae from taking over your aquarium with some simple steps. Without much ado, let’s get started!

Note – This part 2 of the Algae Control series, the rest of the series can be found here:-

What Is Brown Algae?

Diatoms or brown algae as it is known are brown or golden-brown in color. They actually aren’t classified as algae at all, but are considered tiny, single-celled organisms.

They are one of the most common algae found in new tanks because they thrive on the silicate that comes from the water you’ve put in.

Brown Algae/Diatoms

Brown Algae/Diatoms

They tend to go away as the silicates in the water get consumed. If you have silicates in your tap water though, that isn’t being filtered then this can be an ongoing problem that you’ll have to tackle.

Thus, it is important to cycle out your tank after initially setting it up with water.

Advantages And Disadvantages Of Brown Algae




  • They can make your aquarium look pretty nasty.
  • They consume vital nutrients that are required by your fish, plants and corals.
  • Brown algae can block the view of your fish by growing on the tank walls.

Ways To Identify Brown Algae

Brown algae is encased in a hard skeletal structure that is made up of silicone dioxide. These skeletal shells interlock with each other to form large masses of brown algae.

Diatoms/Brown Algae On The Tank Bed

Diatoms/Brown Algae On The Tank Bed

As the name suggests they are brown in color or golden-brown at times. They form large thin dust or dirt like beds that cover anything right from your rocks, corals or even your wall tank.

Causes For The Growth Of Brown Algae

During the initial cycling process of your aquarium it is natural to find brown algae growing inside.

During this cycling phase your water has high levels of nitrate in it which causes the brown algae to thrive and they begin to diminish as the cycling phase is over.

After the cycling phase is over it is possible for the brown algae to have not gone away if certain measures have not been taken such as:

1. Silicate In The Water

    The presence of silicate in the water even after the cycling of your aquarium can be one of the reasons why the brown algae is still there. Brown algae thrives in the presence of silicate since a majority of its structure is made up of silicate. Silicate can also originate from the sand in your aquarium or the sea salt mixes that you’ve added.

2. Presence Of Nitrates

    Besides silicates, brown algae requires nitrogen in order to survive and reproduce. Nitrates enter the aquarium through the nitrate cycling process, sea salts, water and food given to the fish.

3. Lighting

    Poor lighting in your aquarium can result in the growth of brown algae. If your aquarium is has limited light for prolonged periods, it can lead to the growth of brown algae in your saltwater aquarium.

Ways To Control Brown Algae

During the initial cycling process of your aquarium it is natural to find brown algae growing inside. During this cycling phase your water has high levels of nitrate in it which causes the brown algae to thrive and they begin to diminish as the cycling phase is over.

In certain cases when some elements aren’t kept under control they can continue to grow long after the aquarium is established.

Let’s take a look at what we can do to limit and eradicate the brown algae from your pretty little tank.

1. Change The Water Regularly

Nitrate levels can build up in the water over a period of time and accumulated sea salt mixes, food and from the original source of water as well, so it is important to change the water in your tank on a monthly basis.

Regular Water Changes (pix source)

Regular Water Changes (pix source)

Regular water changes ensures that fresh water coming into the system and the old water with silicates and nitrates are being filtered out.

2. Clean The Filter

Filters need to be cleaned out on a regular basis to ensure that it does its job properly. If there’s a lot of dirt and gravel collected in the filter it restricts the flow of water into the system and over a period of time some of the dirt tends to get through the filter.

Clean your filters! (pix source)

Clean your filters! (pix source)

Cleaning the filter will make sure that clean water is regulated properly.

3. Increase Lighting

You’ll see brown algae growing in areas in your aquarium that receives less lighting. If the whole of your aquarium receives less lighting then your whole aquarium is susceptible to brown algae. Keep the lights on between 8 to 10 hours a day.

Keeping the lighting on for less than 8 hours can increase the growth of brown algae and keeping it on for more than 10 hours will bring other, unwanted forms of algae into the aquarium.

4. Clean Your Aquarium

Removing the brown algae with the use of a brush with soft bristles can prevent the immediate spreading of the algae. Check for brown algae on a regular basis and clean the rocks, coral or the glass walls to keep the aquarium clean.

This will control the spreading of the brown algae for the immediate future but not in the long-term. This has to be followed up with the other control measures listed here to make sure that it doesn’t come back.

5. Reduce Silicate Content

Sea salt mixes, sand and unfiltered water can be sources of silicate in your saltwater aquarium. Look for a different sea salt mixture that does not have silicate contents in it.

Certain types of sand have excessive silicate than what is normally found in sand which can be controlled by buying the right kind of sand from your pet shop.

6. RO/DI Water

Don’t use your tap water to fill your tank as it contains high amounts of silicate.

Using reverse osmosis or distilled water, which is free from nitrate and silicate, will limit the amount of nitrate and silicate getting into your tank.

7. Don’t Overfeed Your Fish

Overfeeding your fish will leave the uneaten food in the aquarium for days and this leads to a build-up of nitrates in the water. Fish food are high in nitrates which is something brown algae thrive on.

Feeding your fish adequately will stop the additional nitrate from unnecessarily dissolving in the water.

8. Clean Loose Waste

Loose waste can accumulate over a period of time in the tank which contribute towards the increasing nitrates in the system.

Loose waste such as uneaten food and detritus from the substrate should be cleaned from time to time.

9. Vodka Nitrate Reduction

This new method of reducing nitrates has become quite popular among fishkeeping enthusiasts. Many people have found that adding small amounts of vodka to the aquarium can reduce nitrate (as well as phosphate) levels significantly.

No, don't turn your aquarium into a giant cocktail

No, don’t turn your aquarium into a giant cocktail

1.2ml of vodka (40% alcohol) per 100 gallons is what is required to be administered everyday. Nitrate and phosphate levels are said to reduce significantly in a matter of 48 hours and people have reported a success of seeing a majority of the brown algae disappearing by then as well.

10. Placing Mangrove Plants In The Aquarium

Mangrove plants are a great addition to the aquarium for those people that want a more natural way of removing nitrogen from their saltwater aquarium. Mangrove plants not only absorb the nitrates in the water, but also phosphates and other organic substances that help the growth of algae in your aquarium.

It also means that you wouldn’t need to tend to your aquarium as often as you would with many other control methods. As a matter of fact many people use mangrove plants as a substitute for their protein skimmer as the protein skimmer tends to do lesser work with the introduction of mangrove plants into the aquarium.

Share The Knowledge

Putting some or all (if required) of the control methods mentioned above into practice will remove any signs of brown algae in your saltwater aquarium. Follow the techniques carefully and watch your aquarium blossom into a beautiful ecosystem.

We’d love to hear about how you manage to control brown algae in your aquarium, what techniques work for you and if you’ve encountered any new techniques that we don’t know of. Feel free to share your experience with us in the comments section below.

About Dennis Hanson

Dennis is an experienced aquarist with many years of knowledge and experience in keeping successful tanks. He also has no relations to the pop group Hanson.

15 thoughts on “Saltwater Algae Control: Brown Algae

  1. Pingback: Saltwater Algae Control: The Ultimate Guide | Home Aquaria

  2. Reply Brinda C Jun 25,2014 5:12 pm

    Do NOT do the vodka. Killed all my fish and clouded whole tank. Had to drain whole 100 gallon tank! Not happy.

  3. Pingback: Brown sand bed

  4. Reply GARRY Y Mar 9,2015 8:02 pm

    You didn’t dose properly wouldn’t cloud the tank in anyway shape or form!

  5. Reply Mark Mar 19,2015 7:35 am

    how much vodka would I dose for a 30 gallon tank?

  6. Reply Dave Apr 14,2015 6:52 pm

    Dosing Vodka can easily cloud your water with bacteria blooms, however, this should not have killed your fish. I suspect something else killed your fish or perhaps a combination of things and yes maybe the bloom did add stress to them and they perished.

    I agree with Garry you must have used too much. You need to start off slower I would advise using just .5ml per 100 gallons and work your way up.

    Mangroves just dont work, I think that was a poor suggestion by the author. They infact do not absorb as much nutrients as one might think and they are difficult to maintain. I suggest using a different Macro algae instead.

  7. Reply B Jun 1,2015 9:55 pm

    How much vodka would you suggest for my 180 litre tank? The red/brown dust is everywhere!!

  8. Reply Kenny Dec 9,2015 6:56 am

    If you are wanting to Vodka Dose this is the best site to learn more about how to do it…..

  9. Reply brown green and purple algae growth on rock and fd Apr 13,2016 1:40 am

    I have treated my tank with recomended doses for a 75 gallon salt. 3 times now i have this green and brown stuff on the live rock and on the feather duster it was green then turned purple.what is going on and how can i fix this my test strips are always on the spot right colors.

  10. Reply brown algae May 15,2016 5:49 pm

    why is brown algae a plant?

  11. Reply zeev schmidt Jun 10,2016 12:59 pm

    thank for your advice ,going to give it a try ,zeev schmidt

    for my freshwater aquarium .

  12. Reply trevor Sep 3,2016 6:01 am

    Wouldn’t a refugium work here?

  13. Reply Harry Ehlers Oct 28,2016 5:14 pm

    How do I rid my tank of dark brown algae (not diatoms)?

  14. Reply natasha Feb 10,2018 1:54 am

    “brown algae and diatoms are not really considered algae”…im sorry, but yes they are. I am shocked that this was even stated.

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