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How to get rid of Brown Algae (Diatoms) in Reef Tank

To set up a new reef tank, you must install a live rock, arrange it appropriately and include a right arch at the center of the substrate.

After that, you must put the corals in the best position to avoid offending each other. You can go ahead by acclimating carefully the best invertebrates and fish before turning them loose in your reef tank,

However, all things may seem to work well for a few weeks until you start seeing a brown covering. Such covering is known as brown algae or diatoms.

What is Brown Algae?

Brown algae (diatoms) is a unicellular organism which is brown in color, bony in structure and comprises of silicon nitrate.

Brown algae can appear in a reef tank which has just completed its cycle and also an established one. It usually grows as a thin layer on the substrate, glass, pumps, rock, sand and any other surface in the reef tank. It is good that you remove the brown algae from your reef tank due to the following reasons:

  • They can cover the live rock and corals making them suffocate and die.
  • When the brown algae decompose it releases silicates back to the water. These cannot work well to your creatures.
  • When left for a longer time it can be difficult to remove them from the aquarium wall and rock.

The root causes of brown algae in reef tank

Video: “How To Kill Marine Aquarium Brown Algae & Diatoms”

After knowing the reason why you should remove brown algae you can then find out the root causes. You should also identify the root cause before you decide on how you are going to remove them. Some of the things you should consider when identifying the root causes are:

High phosphates

Phosphates are vital nutrients for all living things. Since every aquarium has phosphates you cannot do away with them completely from your tank.

However, you should avoid a high level of phosphates as they boost the growth of brown algae. You can keep checking the phosphate level in your reef tank and if possible, keep it at 0.03 ppm.


You should avoid build-up of nitrate in the reef through regular water changes. This is because brown algae love to eat nitrates. You can maintain it at least 20 ppm. You can introduce nitrate absorbing filtrates in the water filter.


These are usually gotten from sand, additives and salt mixes

Premature live rocks

Adding a live rock which is not cured completely can be a breeding ground for brown algae.

How to get rid of brown algae in reef tank

One of the major ways on how to get rid of brown algae in reef tank is by limiting these root causes. Some of the other ways you can achieve your strategy of removing brown algae are:

Changing water

One of the best ways on how to get rid of brown algae in reef tank is by changing water regularly. By changing the water in your tank, you will remove phosphates and nitrates which are eaten by brown algae.

Ensure you get deep down your tank using a gravel vacuum. This is because fish waste usually falls down the floor and sinks deep inside the gravel. By getting out this waste you will make the brown algae to starve and die from hunger.

When changing water, you can use a small brush in removing carefully much of the brown algae from the surfaces and rocks. You can also vacuum any bits of brown algae which may be floating on your reef tank.

However, the easiest way to follow in this by tieing your old toothbrush to the end of the siphon hose. When you dislodge the brown algae will be sucked up instantly into your hose pipe.

Reverse osmosis water

Video: “How to Set up an RO/DI Unit for Fish!”

You can also use Deionization and reverse osmosis water filter when changing water. Having these filters will ensure that no toxic compounds, heavy metals and pollutants will reach your reef tank.

By filling your entire tank and changing water using DI/RO, all the water problems that you face will be reduced drastically. The best thing about these methods of changing water is that they do not contribute to brown algae growth supplements.

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Algae eater

Another way on how you can get rid of brown algae in reef tank is by introducing aquatic species into the tank. Below are some of the species which eat brown algae.

Amano shrimp

They can eat brown algae and any other algae which grow in a reef tank. However, they cannot clean any glass in your tank.

Nerite snails

They can eat brown algae. All they do is to scour the surface of the tank but they do not eat any other plants growing inside the tank.

Bristlenose plecos and otoclinus catfish

which may or not eat the brown algae.

Margarita snail

These creatures can completely devour any brown algae in the saltwater.

Scrubbing brown algae from the tank

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In this case, you will use a scrubbing pad which does not have any added soaps or cleaners. A plain scrubber is the best in removing brown algae.

To effectively remove the algae you will also require a small bucket of water and then follow the steps below.

1Place the scrubbing pad in your hand and put is above the substrate.
2Maintain steady pressure on your scrubber as you pull your hand up the waterline.
3Take the scrubber out and squeeze it onto the bucket.
4Continue repeating this process until your reef tank is clear.
5To remove more brown algae you should wipe your tank from bottom to top.

Increasing water flow

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Having random, strong water flow into your tank will be of great benefit to your creatures and can assist in controlling brown algae. When water flows randomly and continuously into the tank, brown algae cell will not get time to attach onto rock or sand.

In case there is any which has grown it will be suspended on the water. This can offer it a good chance of being passed to the filtration area and can be removed easily from water.

Avoid overfeeding

One of the elements which can increase brown algae in your tank is overfeeding your creatures. Thus, you must ensure that you offer your reefs enough food which they can eat within a few minutes.

Placing a lot of food which your fish cannot finish will act like an organic waste. Having more waste in your tank will increase the chances of having nitrates, silicates and phosphates.

Ensure that no food particles sink to the bottom of the tank and if they do you should remove them immediately.

Reducing light

Brown algae usually thrive well where there is a lot of light. Thus, you can switch off any lighting around your reef tank for about 3 days. If you do so be assured that 99% of the brown algae will die and the few which may be remaining will be a weak state. Thus, you can easily remove them manually.

Using industrially manufactured chemicals

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In case you have tried all the non-chemical ways and they seem not to work well, then you can try to use powerful chemicals manufactured in industries. You can ask for algae experts to offer you a recommendation of the best chemical that you can use. Be assured that when you get a powerful chemical it will act as a reset button. This is because it will be able to kill almost all the brown algae in your reef tank.

Some of the advantages of using these chemicals are:


  • They can kill both small and large brown algae in your reef tank without using antibacterial agents, phosphates or algaecides.
  • They do not harm any other inhabitants in the aquarium
  • Do tamper with the balancing of water nutrients. Instead, they assist in balancing it.


As you try to deal with brown algae, you should remember that they are common in many reef tanks. Regardless of how hard you will try, be assured that you encounter the algae at least once. The only thing you should ask yourself is how best can you handle this situation which is difficult to avoid.

However, through dedication and patience you can win this battle of removing brown algae. Remember if you keep ignoring the brown algae in the reef tank it can spread quickly and become difficult to be removed. The sooner you start to remove it the better for you.

Many people have followed the above tips on how to get rid of brown algae in reef tank and they have found them to be very useful. Be assured that you will have a brighter smile after following these guidelines since you will have a clear tank free from brown algae.

Aaron Boyd
Aaron Boyd

Hello, I’m Aaron Boyd, the proud owner and author behind Aqua Movement. I hope my article was able to answer your questions. If you want to learn more about me, click the home icon above.

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