Brown algae within the aquarium: the best way to lastly do away with them

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Seeing algae in your tank may seem like the start of an uphill battle, but luckily, the most common type of brown algae is usually the one that goes away the fastest. Brown algae, usually a type of diatom, can create a rusty coating over the sides, substrate, decorations, and plants in your aquarium. Like most algae, brown algae are likely to be found in bike and young tanks.

Read on to find out everything you need to know about brown algae, what causes brown algae, and how to remove it if it ever shows up in your aquarium!

What is brown algae?

Brown algae are easily identified by red (Rhodophyta) or green (Chlorophyta) algae, although the exact species you are dealing with can only be determined under a microscope. Real brown algae are a member of Phaeophyta, although they cannot be found in the aquarium hobby. This type of brown algae is found in the cooler waters of North America and forms some of the largest kelp forests.

But what do brown algae relate to in the aquarium hobby? Most of the time, when someone says that your tank is struggling with brown algae, it means you have a diatom problem. Diatoms are an integral part of aquatic ecosystems and are responsible for supplying most of the available oxygen on the planet.

These unicellular algae have cell walls made of silica that protect them from pathogens. They are planktonic and their movement depends on the currents in rivers and oceans. They cannot float freely for long in the aquarium and get caught on plants and substrates, which cover these objects with a rust-colored mat.

What do brown algae look like?

Brown algae make things look dirty. You may notice rust-colored stains on decorations, plants, and the substrate. As long as these algae don't get thick, clumped and / or change color, it's safe to say that your algae problem is simply diatoms.

Are brown algae good or bad in an aquarium?

Brown algae are not good for the aquarium, but they are not necessarily bad either. As mentioned earlier, diatoms have a silica cell wall; This means that they need a constant source of silicates in order to repair their structures and reproduce.

Most aquariums have limited amounts of silica available, and diatoms usually go away on their own within a few days or weeks. However, if you have a persistent diatom problem, this brown alga could be a sign of a serious underlying problem that we will address later will go into more detail.

What causes brown algae in aquariums?

There are a few reasons these rust stains might show up in your aquarium. The most common reason is that the tank has been set up again. However, this can also be due to poor tap water quality, certain substrates, or light and nutrient imbalances.

New tank setup

For the first few months after running an aquarium, there is no telling what your tank will do next. Parameters are usually found everywhere, the turbidity of the water changes from day to day and the idea of ​​a stable system seems unattainable and far in the future. During this time, however, many useful bacterial populations establish themselves and work to create this ideal stability.

The problem is that this beneficial bacterium takes time to colonize sufficiently to absorb all of the extra nutrients that are available in the water column. This means that more beneficial species like brown algae can come in and thrive; The problem, however, is that there is only a limited amount of silica available.

For a few days or a week or two, diatoms will take over most of the surfaces in the aquarium, taking in nutrients that the beneficial bacteria cannot process quickly enough. But once the silicate is used up from the system, the diatoms leave; They are unlikely to return unless you are dealing with one of the following causes.

Does brown algae mean your tank is being driven?

While a brown algae outbreak doesn't mean your tank is being driven, it definitely means you are on the right track. As annoying as algae outbreaks are, they are a sure sign that something is happening in your tank and that soon enough you will be able to add the fish and invertebrates of your dreams!

Tap water quality

Water changes are essential for good aquarium maintenance. They remove excess and depleted nutrients and introduce new trace elements and fresh oxygen.

Most freshwater lovers like to use tap water because most of the essential minerals are already there. However, tap water is notorious for having many unknowns, and it is usually safe to assume that some amount of phosphate will get into the system through water changes. Without a silicate test kit or a full analysis of your public water, it cannot be determined whether or how many silicates are in your tap water. This means that as long as you are using this water, there is always a chance that brown algae will show up in your tank.

Many saltwater hobbyists use distilled water or reverse osmosis (RO) water by default to reduce the likelihood of such contaminants entering the system. While this may require a few additional steps for freshwater tanks, it may be the best option to avoid algae in the future.


While substrates typically do not cause problems, some have been known to leak silicates in the past. Silica is actually the main constituent of sand around the world, which means there is a good chance it is in your substrate too.

If you've recently changed your substrate and you are seeing diatoms, this is something to consider. Otherwise, you shouldn't have any issues with excess silica in your system as long as the substrate is labeled aquarium safe and has trustworthy ratings.

Light and nutrient imbalances

It is known that light and nutrient imbalances are responsible for most algae problems, and diatoms are no different. In addition to silica, brown algae also need nitrates and phosphates in order to really thrive in the aquarium.

In both freshwater and saltwater aquariums, nitrates and phosphates are essential nutrients that fish and other organisms need to perform bodily functions. While it seems like 0ppm is the answer for everything, you actually want traceable amounts of phosphate and nitrate in your system, especially if you have live plants. However, if these nutrients are not absorbed quickly enough, or if too much gets into the system in large quantities, brown, red, and green algae can begin to outperform living plants and corals.

Just as silicates can get into the tank via tap water, nitrates and phosphates can also get into the tank via water changes. If you find brown, red, and / or green algae popping up in your tank on a regular basis and there is no other likely explanation, it may be best to look into options for distilled and RO water as the problem is most likely im Water lies you used.

In addition to nutrients, excessive light is an important catalyst for algae growth. In the fish farming hobby, however, there is some debate about whether diatoms thrive in strong or weak light. One side believes that diatoms colonize faster in low light, as they can outperform many other light-hungry species of red and green algae, as well as the living plants in your aquarium. The other side believes that diatoms are efficient photosynthetic algae that grow and spread the fastest under longer and more intense lighting conditions.

You may get advice that a temporary blackout to your tank will help get rid of the diatoms. However, we recommend just waiting.

How do you get rid of brown algae in an aquarium?

Of all the red and green algae, brown algae are probably the easiest to control. Diatoms are usually found in newly set up aquariums as they feed on the available silicates and other excess nutrients in the aquarium. However, once these are used up, the diatoms can no longer grow.

But when you're facing a chronic brown algae outbreak that never seems to go away, how can you get rid of it forever?

Tank maintenance

One of the best ways to remove brown algae, green algae, red algae, or other mysterious types of algae that get into our aquariums is to spend a little more time on maintenance. A brown algae problem results from poor water parameters, which can often be remedied with just one series of regular water changes with high quality spring water.

At the same time, you'll want to remove decorations and plants covered in diatoms and gently scrub them in an external container. This will prevent spores from spreading and potentially returning even stronger in other areas of your tank. If you have diatoms covering the substrate, you should also make sure that any particles floating in the water column are vacuumed and vacuumed.


While some fish and invertebrates will eat brown algae, they are not the best way to get rid of algae because it cannot fix the underlying problem. However, if you have ample tank space and want to add some algae eaters to your cleaning crew, there are a few species that will specifically take care of diatoms.

For fish, Otocinclus are some of the best aquarium cleaners. They need to be kept in schools ages 6+ and can be shy so they will need a lot of decorations like plants and driftwood. In snails, ram snails (family Planorbidae) and nerite snails (family Neritidae) fight uneaten food, rotting plant leaves and even eat diatoms directly. There can be some issues with Ramshorn overpopulation, but Nerites need salt water to breed so you are safe from a tank overflowing with snails. Amano shrimp can also help keep the water in the aquarium clean by picking up loose waste.

Additional plants can also be added if the tank is properly adjusted. Some plants, especially floating plants, are known to be able to absorb excess nutrients faster than some algae.

Chemical alternatives

There shouldn't really be any reason to turn to chemical alternatives to remove brown algae, but if you want to quit the hobby because of some diatoms it is definitely worth a try!

There are several aquarium-safe products that can be used to remove phosphates and silicates from the water column. These solutions must be dosed according to the instructions. However, it is important to note that such products are intended to rid the water column of these target nutrients. This means that plants and other nutrient-dependent organisms can suffer as their source of essential nutrients has been depleted.

Some hobbyists also turn to hydrogen peroxide to target areas of brown algae, while others dose all-in-one products that specifically target algae and protect other plants and animals. While these products may work for some, we definitely recommend creating a water change schedule and performing regular tank maintenance first!


Brown algae can be frustrating and ugly when they take over your aquarium. Fortunately, this type of algae is one of the easiest to treat and is usually due to a newly established aquarium, poor tap water quality, certain substrates, and / or light and nutrient imbalances.

Usually all that is needed to get rid of brown algae is more regular maintenance so that the tank water parameters are tested where they should be. Some hobbyists even allow brown algae to exhaust themselves as they absorb all of the extra silicates and phosphates in the aquarium. However, if your brown algae don't want to go, it may be time to introduce algae-eating fish or invertebrates and turn to chemical alternatives.

If you have any questions about brown algae or other types of algae, or if you have experience cleaning up a particularly stubborn brown algae problem in your own aquarium, please leave a comment below!

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