Brown algae is a very tiny little animal called a diatom. This creature is so small that it cannot be seen without the use of a microscope. Now you might want to ask if I need a microscope to see it, then why on earth is brown algae visible in my tank? Well to answer that, “brown algae” is made up of billions of tiny interlocked diatoms. Now if you wanted to get technical, brown algae is a bacterial colony and not that it makes you feel any better about the brown film covering the inside of your tank. 

How do you identify brown algae?

Brown algae always form in soft brown clumpy patches. Brown algae as you all know, is very poor in swimming and instead prefers to attach itself to a stable surface in your tanks such as the glass, substrate or even plants and decorations. The soft, slimy structure can easily be removed by lightly rubbing it gently with your finger.

What is the thing that causes brown algae to appear in your tank?

Consider it a rite of passage that the brown algae often appears whenever cycling and maturing are taking place in your new tank. Brown algae are something that every rookie tank owner has to endure with, and the problem generally resolves itself within months. But that is not the only time it pops up. Brown algae are part of the world’s ecosystem. But if your brown algae are growing out of control then definitely you may be encouraging its growth with the following:

(1) Presence of Nitrates

If there are no more silicates left, brown algae can as well survive on nitrates in the water.

Potential sources of nitrates in your tank:

(1) Tap water and well water

(2) Plant fertilizers (nitrate is often the main ingredient)

(3) Fish food

(4) Decaying plant matter

(5) Fish poop

(2) Poor lighting

It is also commonly thought that low light levels are also part of the things that can contribute to a brown algae outbreak. Brown algae aren’t just algae but also diatoms; lighting isn’t considered a major contributing factor to its appearance. As long as the water has silicates, brown algae are just as happy to grow in a dimly lit tank as also it is in a bright one.

However, many publications continue to list little light as a cause for brown algae growth. 

(3) Silicate in the water

Silicates are considered to be the number one of the primary cause of brown algae blooms. To put it merely, silicates are diatom’s best food. They find it very delicious and will happily thrive and reproduce in any tank that is high in silicates.

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Potential sources of silicate in your tank:

(1) Tap water and well water

(2) Salt mix

(3) Live rocks

(4) Live sand

(4) Presence of phosphates

Potential sources of phosphates in your tank:

The most common phosphates source comes from wastes as they are broken down in your aquarium or tank. 

(1) Uneaten fish food

(2) Plant decay

(3) Dead algae

(4) Fish poop

(5) Dead fish

(6) KH and pH Buffers

(7) Tap water and well water

Brown algae don’t care whether your aquarium is either freshwater or it is saltwater. Still, if your aquarium has a good source of the above nutrients, you are laying out a welcome mat.

Brown algae in fish tank good or bad?

The answer is No. Brown algae are considered to be very harmless to your fish, and it won’t kill them.

Brown algae could leave your fish healthier than you can ever imagine. You see, the diatoms that make up brown algae feed on CO2. They then release pure oxygen, which increases the dissolved oxygen levels in your tank or aquarium. All aquarium owners know the importance of well-oxygenated water. Fishes that feel comfortable with brown algae in the tank understand that the oxygen levels in your tank are relatively too low. For the most part, fish don’t even care about the brown algae and happily swim in a tank with a good coating of the brown gunk. But I have bad news for those of you with reef tanks or planted tank. Brown algae aren’t as forgiving to your fish’s environment as you think. If you notice brown algae coating, your plants or coral don’t ever leave it sitting too long. While brown algae won’t kill your plants and corals just by coating it, it will compete for nutrients and immediately start block out sunlight from entering your aquarium which can eventually result in your aquarium’s death plants.

How to get rid of brown algae in fish tank

Dealing with brown algae isn’t tricky at all. In most cases, brown algae problems clear up on their own without any action being carried out. If you are sick of the death of staring at the brown slime, then follow the steps below to get your brown algae problem under control without causing harm to your tank or aquarium. Remember to thoroughly wash your hands and remove any jewellery before placing your hands inside your fish tank as it may be detrimental to your fish’s health. 

How to remove brown algae from the glass of your tank.

It doesn’t even matter whether your fish tank is glass or acrylic, and brown algae that coat the walls of your aquarium can be wiped away immediately. The trick here is to use a single smooth wiping motion from top to bottom. By doing this, you are “scooping” so that all little brown algae as possible will float off into the water of your tank. I have experienced the most success with a small squeegee for swiping away the brown algae on the front of my tank.

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However, a simple cloth/sponge and a steady arm can work just perfectly as well.

How to stop brown algae from coming back to your tank

Once you have removed all the brown algae from your tank or aquarium, you must now want to ensure that the environment in your tank isn’t encouraging it to make a comeback. If you are an expert, you can skip this section and then you will likely have an appropriate routine to maintain the very best water quality. But if you are new to aquariums, then the following tips can help prevent brown algae from making a comeback in your tank. 

Step 1: Adequate filtration

I know it may seem obvious, but I have seen it times without number and beginner hobbyists using the wrong filter for their tank. Proper or reasonable filtration set-up plays a vital role in a healthy fish tank. Please make sure you check your filter to ensure that it is rated for your aquarium’s gallon/litre capacity. While you’re at it, make sure your filter is clean and functioning in the proper matter. If nitrates (from dead organisms and uneaten food) are a problem to you, you may also want to invest in a protein skimmer, which also helps prevent algae build-up and aLeo assists with the keeping of your water crystal clear.

Step 2: Water Movement

To discourage brown algae diatoms, then you need water movement. You see, diatoms are very terrible swimmers. This is why they like to bulk up or coat everything in your tank. If the water is moving, then diatoms have difficulty clumping together and anchoring themselves onto the surfaces in your tank. The added water movement will also ensure that all the water in your tank is filtered away instead of just a portion of it. Water movement method can be achieved by using a powerhead or current maker.

Step 3: Water change

Note that: water changing should already be part of your aquarium maintenance routine. However, the water you are using may be a significant contributor to brown algae in one way or the other. Tap water also well water can have high concentrations of the nutrients that brown algae love to eat. So the reasonable question is “how do you prevent your water change from encouraging the growth of brown algae?. The most favourable action is to adopt the reverse osmosis water in which has had its impurities removed immediately. RO water is also known as DI water. While you can buy RO water in bottles, the cost will quickly add up. It is cheaper to “make” it yourself using a Reverse Osmosis filter system.

Step 4: Don’t overfeed

Let’s take a look at that excess food that falls to the substrate of your tank? If not taken care of properly that fish food will rot and releasing nutrients that brown algae love.

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Step 5: Avoid all sources of silicates

Since silicates are also part of the significant contributor to brown algae blooms, then you should avoid introducing them to your tank when possible.

Every time you add something new to your tank, make sure you check the ingredients. Live sand, salt mix and silica sand may contribute to an abundance of silicates in your water which isn’t a good thing for your fish.

Other methods to get rid of algae in your tank

Introduce fishes and critters that feed on brown algae

Alternatively, you can introduce fishes to your environment that enjoys or eat algae. Also note that: this should only be your last option. Adding a live creature to come to solve your algae problem comes with its own set of challenges, including:

(1) Does it play nice with your other fish?

(2) Will it survive in your ecosystem?

(3) Will it eat brown algae or your fish food?

(4) What do you feed it once the algae have gone?

(5) How do you care for it?

(6) If you still want to go ahead and introduce a brown algae eater to your aquarium, then you can choose from the below list:

Freshwater algae eaters

(1) Amano shrimp

(2) Ramshorn snails

(3) Nerite snails

(4) Twig catfish

(5) Bristlenose pleco

(6) Siamese algae eater

(7) Malaysian trumpet snail

Saltwater algae eaters

(1) Blennies

(2) Trochus snail

(3) Kole tang

(4) Emerald crab

(5) Tangs

Brown diatom algae 

Diatoms are unicellular algae (Class: Bacillariophyceae) that consist of many species that all possess a cell wall made of silica. They are photosynthesizing, which means they can use light to produce their food as are many other types of algae. Their yellowish-brown chloroplasts the site of photosynthesis are what makes them with their golden brown colour. 

Diatoms are mostly found in the oceans, lakes, ponds, rivers, and even in damp soil and also that mud puddle in your backyard. In other words, they are found anywhere there is enough water. Masses of diatom skeletons made of silica have been preserved on earth in such large quantities that they have formed deep deposits that have been harvested and used for different purposes as in filters, paints, toothpaste, funny right?? (think about that the next time you’re standing in front of the bathroom mirror polishing your pearly whites), and many other applications therein. 

Why Remove Brown Diatom?

There are so many reasons to remove them from your tank and keep them from reappearing in the future, other than the fact that brown diatoms are usually ugly in an aquarium.

(1) They can deplete oxygen in the tank when they die and decompose in it. 

(2) They can cover the corals and live rock, suffocating them and causing them to die-off.

(3) As the diatoms decompose, they tend to release silicate back into the aquarium water.

(4) They can be tough to remove from the rock and aquarium walls.


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