How To Handle Brown Algae In An Aquarium?

Brown algae is classified as a certain type of algae that’s capable of making the water in your tank turn a brown color.

It can be caused by various different factors, and this algae itself can cause various different effects in your tank if it’s not taken care of properly. Not only that, but it can make the water in your aquarium turn a brown color, which just looks unappealing.

brown algaeGiven the negative effects of having algae that’s brown in your tank, you should engage in the measures needed in order to remove it. But it can be difficult to know how to get rid of it, especially if you’re not familiar with algae in general. Because of that, I’ve put together a guide for your benefit that may help you learn about algae in general as well as some helpful information about removing and preventing this type of algae from occurring in the future.

Before going any further, consider starting from our home page to find out how to maintain your aquarium


What is Brown Algae?

This type of algae is classified as the largest and most complex type of marine algae, and it’s distinguished from other types because of the fact that it contains Fucoxanthin. This element is known for its ability to only be present in algae that’s brown, and it’s the element that’s responsible for giving this algae its brown and darker color when compared to the other types.

There are around 1,800 different species of the algae, and they typically include plants like complex forms of seaweeds. They’re typically found in waters that have a brackish element, and they can be found in both freshwater or saltwater aquariums. Each species of browned algae contains several common elements, including chrysophytes, synurophytes, and even diatoms (1).

Perhaps the most common type of browned algae is classified as kelp, but there are various other types including rockweed or wracks. Since they commonly grow in marine environments, they can be consumed by certain herbivorous organisms in these waters, like fish, gastropods, and even sea urchins. Some humans are even known to use them for certain food additives, like food thickness or stabilizers. 

Before going any further, check out our page on the best hob filters. Setting up a hob filter is a good a way to keep a healthy clean tank. 

Why Does it Grow?

Browned algae has the ability to appear in your tank for a variety of reasons, but most people that experience them are usually first beginning their new tank’s processes. Practically everyone that starts out a fish tank has to deal with their aquarium environment experiencing this algae at some point in the beginning processes. Aside from that, there may be a few other specific reasons why your tank has browned algae in it.


Your tank water likely has an over-abundance of silicates in it because this occurs when there isn’t enough lighting coming into contact with the water. Silicates have the ability to cause your tank to grow browned algae because they act as one of the algae’s favorite food. More specifically, since diatoms love to consume silicates, having an excess supply of them in your tank water can encourage the diatoms to grow and spread, essentially causing there to be browned algae in your tank water.

When the diatoms consume a large amount of silicates, they’re able to thrive and even reproduce, which results in the dramatic spread of the algae over only a short period of time. To limit the amount of algae in your water due to your high level of silicates, you should reduce and limit the amount of silicates that are present in your tank water.

More specifically, you probably have too many silicates in your tank because of mixing tap water and well water in your tank, adding a salt mixture to your water, or even when you have either live rocks or live sand to your aquarium.for future reference, you should limit the amount of silicates that your water is exposed to.

Want to get some good floating plants in your aquarium, then you should read this article

Nitrates behind brown algae

Nitrates are classified as elements that can release beneficial bacteria into your tank in order to transform ammonia into nitrites, which can then provide benefits to your fish tank’s ecosystem. From this, it seems like nitrates would be a great thing to have in your tank. But they’re only beneficial when they exist in small and controlled quantities. Having an over-abundance of nitrates can actually be harmful for your tank, and they can even cause the appearance of browned algae in your aquarium.

Browned algae are able to consume nitrates in your tank, so having an excess amount of nitrates is essentially giving the browned algae something to consume and grow from. This would only be the case if silicates aren’t the problem though, since algae prefer to consume silicates.

You may have an excess amount of nitrates in your tank water for a variety of reasons, including nitrates from tap water or well water, from plant fertilizers, an excess of fish food, decaying plant matter, and even from an excess of fish waste. In order to limit browned algae from occurring in your tank, you should limit the amount of nitrates that are in your tank. And you can do so by considering whether any of those factors may have contributed to the high levels of nitrates.

Read this article on causes and solutions of red slime algae


Having an excess amount of phosphates in your aquarium can also cause there to be browned algae growth. Phosphates typically come from any wastes that are in your tank, and algae tend to consume on those waste products. To limit the growth of algae in your tank, you may find it helpful to reduce the amount of phosphates and waste that there are in your tank. This may mean that you have to conduct more water changes, or it may even mean that you should install a more productive filtration system.

Some of the most common causes of having phosphates in your aquarium tank include uneaten fish food, plant decay, dead algae, fish waste, using tap water or well water, and even using KH or pH buffers in your water.

Inadequate lighting

Unlike most other types of algae that thrive in environments that have too much lighting, browned algae are able to survive and thrive in poorly lit environments. In your tank water, if the conditions are off in any way, algae has a chance to grow. But the different types of algaes often have to compete with each other in order to thrive, since one can only survive in the certain conditions, leaving the other types of algae to starve.

From that, green algae is able to out-compete browned algae in tanks that have adequate lighting conditions. But browned algae is able to out-compete other types of algae in the dimly-lit fish tanks. Given that, you should make sure that your tank has an adequate amount of lighting, but not too much (4).

Poor oxygen levels could explain brown algae presence

Not only do poor levels of oxygen negatively affect the fish and other organisms in your fish tank, but it can also negatively affect your aquarium because of algae growth. Since various types of algae are competing with each other to survive in certain aquatic conditions, having low oxygen levels can help browned algae survive. This is because they don’t require a large amount of oxygen to survive, unlike other types of algae.

To limit the growth of browned algae due to low oxygen levels in your aquarium, you should increase your oxygen levels. They may be low for various different reasons, including overcrowding, an increase in water temperature, a lack of water movement, an over-abundance of fish waste, low lighting and live plants as well as the use of certain types of chemicals (5).

Quick video on how to fix and remove the brown algae from your aquarium:

Consequences of Not Removing Algae

Even though browned algae isn’t capable of harming your fish at all, it can have negative impacts on the environment of your tank. More specifically, browned algae are capable of consuming carbon dioxide and releasing oxygen in the water, which can actually benefit the fish that are in your tank. This algae can cause your fish to breathe better by having increased oxygen levels.

But if you have live rocks or live plants in your aquarium, they aren’t able to benefit as much. For instance, browned algae can block out your plants and live rocks from having access to the nutrients and sunlight that they need in order to survive. This can not only negatively impact them, but it can eventually kill them if you leave the algae sitting for too long without removing it (3).

How to Remove Brown Algae

To remove browned algae from your tank, you’ll likely need to physically scrub the algae out of the tank. For that, you’ll need some type of scrubbing pads that you can purchase at most aquarium or pet stores. Depending on where the algae is placed in your aquarium, you should scrub it off of the sides of the glass in the aquarium using a steady motion with the scrubby while the water is still in the tank. After a few seconds of scrubbing, you should rinse the scrubby out in a small bucket to prevent the algae from clogging up the open spaces of the sponge.

It can get annoying and tedious to have to rinse the sponge out every few swipes, but it’s the only way that you can remove the algae from the glass without allowing for free-floating algae particles into the water.

If you have algae growth on the fake plants, rocks, or other types of decorations in your tank, you can use a similar but different method. More specifically, you should have bleach, tap water, dechlorinator, a measuring cup, and some buckets handy. When you’re ready, you should mix one part bleach with 20 parts of tap water and then soak the decorations for around 10 minutes. You should then rinse the decorations off and sock the decorations again in a bucket that has tap water and five times the normal dose of dechlorinator in it.

How to Prevent Algae From Growing in the Future

Change the water

The first thing that you could do to remove browned algae from your tank is to make sure that the water is clean, and you can start this by performing water changes more frequently. You shouldn’t change all of the water out of your aquarium, since that may negatively impact the balances of chemicals and the pH balance of the water, but you should replace around 50% of the water with clean water.

When you conduct frequent water changes, it essentially removes the excess nitrates, silicates, and phosphates from the water. From that, the browned algae will have less elements to consume on. And when they’re limited in their consumption supply, they won’t survive and thrive in your tank.

Purchase organisms that consume browned algae

You may find it beneficial to introduce certain organisms to your tank that are able to consume the browned algae so that they can’t spread and become a problem. These organisms can include anywhere from Nerite snails, Amano shrimp, and Otoclinus catfish. Other saltwater species that are capable fo consuming browned algae include Trochus snails or Mexican Turbo snails.

Improve the Lighting

You may find it beneficial to increase the amount of lighting that your tank experiences when dealing with browned algae, since this will ultimately increase the amount of green algae in your tank. That may seem contradictory, but green algae is seemingly easier to control than browned algae, so increasing the lighting will allow green algae to compete with and win overtake the browned algae.

Improving the lighting of your aquarium can also prevent browned algae from growing, since it will help the live plants in your tank thrive. When the live plants thrive, they will take up all of the available nutrients in the water, leaving none for algae to consume.

Increase filtration

You may also find it beneficial to up your filtration methods when you have browned algae, since it will help to clear out the extra organic compounds that the algae was likely consuming in order to survive. You may even find it beneficial to add a sponge filter toy our existing filter, since it will help your filtration processes remove more unwanted elements from the water (4).


Overall, having browned algae in your aquarium tank can cause your tank water to look unhealthy, unsanitary, and unappealing. Not only that, but it can create negative living conditions for any live plants or live rocks that you may have in the tank, since they compete with the live elements for available nutrients in the water.

Given that, you should remove browned algae from your tank once you notice it in there. And you can conduct a few practices in order to prevent browned algae from growing throughout your aquarium in the future by using the methods I’ve provided for you in this article.

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