7 Ways To Stop Brown Algae In Your Fish Tank & 6 Causes

Last Updated on 2023-08-15

Brown algae is a problem in a lot of fish tanks, especially ones that were just set up. Although it poses no threat to your fish, it might make a terrible sight in your aquarium. This sticky film covers the entire tank, including the walls, substrate, ornaments, and plants. Water plants that are coated with this may wither and perish since they can’t perform photosynthesis as efficiently.

There are many different kinds of brown algae, but the stuff many fish tank owners call it isn’t actually algae at all. They are instead diatoms or single-celled algae with walls made of silica. Rocks like quartz and sandstone are two common sources of the silica that makes their way into the water supply naturally.

If you’re curious about brown algae, what causes it, and how to get rid of it if it ever appears in your aquarium, read on!

Table of Contents

What is The Rust Colored Algae In Fish Tank?

Silica algae, also called brown algae, are the rust-colored film that can be seen on the gravel or glass of a fish tank. Commonly known as “brown algae,” diatoms are unicellular creatures that can live either as single cells or in colonies. When grown, they can quickly cover most of the aquarium’s interior in a thin, dark brown layer.

Brown Algae is a sign that the water chemistry of your aquarium is not in optimal balance, but it will not harm your fish if you keep it under control. Like plants and other algae, diatoms photosynthesize light into energy. It is more common in new aquariums, which causes a lot of worry among beginners.

What Causes Brown Algae In Fish Tanks?

Diatoms, a type of brown algae, may spread quickly within a fish tank, and owners might unwittingly spread them by adding new fish or plants. If you don’t find the source of the algae and deal with it, it can come back even after you clean the brown algae bloom out of your aquarium.

Here are 6 of the main causes diatom algae could invade your fish tanks.

1. Diatoms

Diatoms are common sights in a brand-new fish tank. As a result of the nitrogen cycle not being formed and the plants not having had the time to take root, diatoms appear in a young fish tank up to three months following the start of the launch.

2. Silicates

Since diatoms construct their shells from water’s abundant silicates, this element is crucial to their development. You may find silicates in your local water supply, and they can lead to a number of issues. Many fishkeepers believe that sand or other substrates that contain silicon can cause brown diatoms to grow in large numbers.

3. Fertilizers

Overusing fertilizers for aquarium plants can also encourage diatom growth; thus, caution is advised. Indeed, this is most evident in freshwater aquariums.

4. Filter

When the filter is not being used properly, brown algae can also form. It is impossible to purify the water if the filter is clogged or not in use. As a result, organic matter begins to build up.

5. Copper-based Medicines

Large doses of copper- or iodine-containing fish medications can also harm the aquarium’s beneficial bacteria, which can eventually lead to the growth of diatoms. When using table salt for therapeutic purposes, you need to be very careful. The increase in sodium ions will hurt higher plants, but algae will like it a lot.

6. Inadequate Lighting

Dim or no light can also be a game changer for diatom growth. You should turn up the light in this instance. Each day shouldn’t go on for more than 8 hours at the most.

underwater freshwater green landscape / underwater landscape of the lake ecosystem, algae, green water, fresh water

Is Brown Algae In Fish Tanks Good Or Bad?

Brown algae won’t hurt or kill your fish, contrary to popular belief. You may even find that your fish are healthier after being exposed to brown algae. The brown algae’s diatoms are responsible for absorbing carbon dioxide from the air. Pure oxygen is then released, elevating the dissolved oxygen level in your fish tank. Dealing with brown algae isn’t difficult. In most cases, brown algae problems clear up on their own.

Owners of fish tanks are all aware of the need for oxygenated water. Most fish don’t mind swimming in a tank that’s covered in brown algae and will continue to do so if it’s present. Simply being coated by brown algae won’t be enough to destroy your aquarium’s plants and corals, but the algae’s competition for nutrients and blockage of sunlight can be fatal to some of the inhabitants in your fish tank.

How To Stop Brown Algae In Fish Tanks

Starting the fight against diatoms as soon as you see the first signs of their appearance is ideal since doing so later will be much more difficult. Removing diatoms from a fish tank early on does not pose any major challenges.

The ecological balance of a new aquarium can’t be considered to be stable until the algae have settled in and stopped reproducing rapidly (usually, it takes 3-4 weeks). The diatoms will disappear once the ecosystem is back to normal. Starters and other special preparations can be used to kick-start an aquarium, making it easier to achieve a stable ecosystem. All that remains now is to physically remove the algae, either with a sponge or scraper.

Here are several ways to get rid of brown algae in a fish tank:

Take Out the Brown Algae That Has Grown in the Fish Tank

To get rid of the algae, you can use a vacuum cleaner or your bare hands. If the brown algae is left in the aquarium, it will multiply rapidly and be tough to remove.

Provide the Right Lighting

Reduce illumination to just 6 hours per day to aid in algae removal if there are no corals or plants in the fish tank.

The Water Should Be Purified Before Use

Water like this, which lacks nitrates and silicates, prevents the spread of brown algae. Brown algae is often caused by silicates in tap water; thus, it’s important to check that.

Decrease Nitrate Level

 A little vodka in the water will help keep the brown algae at bay. Fish can be harmed by excessive doses of vodka, so be careful. Filtrates that specifically target nitrates can be added to the filter to further mitigate their presence. Keeping the nitrates low is one of the best ways to get rid of brown algae and keep it from showing its ugly head.

Change the Water and Clean the Filter Often.

It guarantees the delivery of pure water, free of silicates and nitrates. At least twice a week, you should clean the aquarium and replace the water. If the algae is becoming a problem, extra cleaning is required.

Stay Away From Salt Mixes With Silicates

In marine aquariums, the salt mix must be carefully monitored. Use rocks and salt mixes that are low in silicate.

Do Not Give the Fish Extra Food

Any food that the fish don’t eat will eventually dissolve into the water as nitrate. Paying close attention during feeding time is an effective strategy for eradicating brown algae. Take two minutes to eat leisurely. Avoid having uneaten food fall to the bottom, where it will be out of sight.

betta care facebook group

What Eats Brown Algae In Fish Tanks?

Fishkeepers have long relied on algae eaters as an important part of their efforts to recreate a natural environment in their fish tanks. In addition to being excellent algae removers, their odd appearance and behavior make them wonderful additions to your aquatic family.

Below are the preferred fish and snails for controlling brown algae in your freshwater aquarium.


Bristlenose Plecos

Bristlenose plecos look like aliens because they have long whiskers that hang down from the top of their heads. The fact that this type of pleco eats algae makes it popular among people who like fish. It feeds on algae and plants that grow in water by sticking its sucking mouth to algae-covered plants and surfaces. So, Bristlenose plecos will do a great job eating the leftover food and brown algae in your tank.

Florida Flagfish

You should definitely get some of these to help keep the brown algae in your freshwater tank at bay. The Florida Flagfish can live in either freshwater or brackish water with cold temperatures and water. Most of the time, Florida Flagfish eat algae and plants, but they also sometimes eat small fry and brine shrimp.


Platies are funny-looking fish that look like clowns. They come in many different colors and patterns, which makes them great cleaners for your tank. Platies eat a wide variety of foods, including algae, plant matter, and even tiny animals. The brown algae in your tank will be easy to get rid of with the help of these easy-to-please eaters.


One of the most popular fish in public aquariums are swordtails. Their popularity comes from the fact that they are calm, easy to care for, and come in many different colors. These tropical fish can live in brackish water and love to eat algae, but you should also give them plants and flake food.

Blue Gouramis

Blue Gouramis are freshwater fish that come in a lot of different shades of silvery blue. Even though Blue Gouramis eat everything, they don’t mind eating all the brown algae in the aquarium to help clean it. Fish flakes and pellets will need to be added to their diet.


Mollies are another type of livebearer that is easily accessible and useful for eradicating brown algae. Mollies are great for first-time fish keepers since they require little maintenance, come in a wide range of colors and forms, and are generally hardy.


Guppies are great fish for people who are just starting out with aquariums because they are easy to care for and don’t fight. Even though guppies are good at keeping brown algae under control, they need to be fed extra food to do well.

The Twig Catfish

The Twig Catfish is another unique algae eater that will make your freshwater tank look nice. Twig catfish eat different kinds of food, algae, and leftovers. This makes them great additions to a freshwater aquarium as long as the right conditions are met. Also, twig catfish do better when there are enough places for them to hide, like caves and plants.

The Otocinclus Catfish

Otocinclus catfish work hard to eat algae and are happy to help you get rid of brown algae. Otocinclus catfish have beautiful rows of armor plating and are usually calm. They can live in most community tanks as long as they have the right conditions.

Siamese Algae-Eater

Siamese algae eaters are great for new fish owners because they keep brown algae from growing in new tanks. As long as they have enough algae to eat, they are easy to care for. You may want to give Siamese algae eaters extra pellets or wafers to make sure they don’t go hungry.


Snail Rabbit

Rabbit snails are a great addition to any freshwater tank since they help keep the tank clean. The rabbit snails will not only beautify the aquarium but also assist keep the brown algae under control. Unlike their more sedentary relatives, Rabbit snails spend their days actively foraging for food.

Ramshorn Snail

You can get ramshorn snails for a low price, and they’re readily available. These gentle creatures spend their time wandering around in search of food. Ramshorn feeds on a wide variety of organic materials, including brown algae, uneaten fish food, and decaying plants.

Nerite Snail

If you need a cleaner for your freshwater or saltwater aquarium, the Nerite snail is your best bet. Most of their time will be spent skimming the surface of your aquarium for algae, especially brown algae, to remove it. Nerite snails are great for starter aquarium keepers since they are low-maintenance, calm, and only grow to be around an inch in length.

Mysterious Snail

One of the most popular additions to freshwater aquariums, mystery snails are a delightful, smaller species of the Apple snail. Mystery snails are slow-moving herbivores that will help clean your tank by consuming dead plants, uneaten food, and many types of algae (including brown algae).

What Eats Brown Hair Algae?

Brown hair algae is a type of algae that can be found in freshwater Tanks. It is usually found in slow-moving areas, such as the back of the Tank. Brown hair algae gets its name from its brown color and long, hair-like appearance. While brown hair algae is not harmful to fish or other aquatic creatures, it can cause problems for tank owners.

Brown hair algae can grow quickly and spread throughout the tank, causing the water to become cloudy. It can also clog filters and impede the growth of other aquatic plants. Fortunately, there are a number of creatures that will eat brown hair algae. These include: 


Plecostomus are a type of fish that love to eat brown hair algae. Also known as plecos or suckermouth catfish, these bottom-dwellers can grow to be more than a foot in length. In addition to eating brown hair algae, Plecostomus also helps to keep the aquarium clean by eating uneaten food and waste. As a result, they are a valuable asset in any freshwater aquarium.

Otocinclus Catfish

Otocinclus catfish are a small species of freshwater fish. These little fish are extremely popular among aquarium enthusiasts due to their peaceful nature and their ability to control algae growth.

Siamese Algae Eater

This hardy fish is often used to control nuisance algae growth. In addition to eating BHA, the Siamese Algae Eater will also consume other types of algae, making it a valuable addition to any freshwater aquarium.

How To Remove Brown Algae From Live Plants

Cleaning live plants isn’t as easy as cleaning plastic or silk because of the risk of harming or killing the plant. They are cleaned in much the same way as synthetic plants, though. Normal maintenance for live plants requires caution, but when it comes to removing algae, you must use extreme caution. You can get rid of the diatoms in your tank by following these simple steps.

1. Loose Debris Removal

To begin, use your finger to carefully scrape away any loose material from the foliage of any living plants. Algae can be removed by simply rubbing or brushing the leaves. The aquarium’s plants need not be removed for this procedure.

2. Use an Algae Pad as a Scrub

You have encountered persistent algae if you see signs of it on the plants after taking the first step. Take out the plants and use an algae pad to scrub the aquarium clean. Scrubbing too harshly can be harmful to plants.

3. Use a Bleaching Agent

The more stubborn the algae, the more challenging it will be to eradicate it. If the previous method failed, then bleaching should be used. For most situations, this is the last resort. To get rid of the algae clinging to your plants, dilute the bleach with water to a 10% concentration. Remember that bleach can kill living plants, so if you accidentally kill any, you should throw them out and start over with new ones.

4. Clean Them and Put Them Back

If you want to keep the aquarium plants alive after you’ve successfully scrubbed the algae off of them, a bath in conditioned water is necessary. Your aquarium plants will be ready to return within about half an hour. For artificial plants and driftwood, you just need to rinse them with water that has been treated and let them dry out before putting them back in the aquarium.

How To Remove Brown Algae From Gravel

When brown algae grow in an aquarium tank, the gravel turns brown. The water in the tank has too much silicates, nitrates, and phosphorus, which makes brown algae grow. How you get rid of brown algae from gravel depends on how big the gravel is.

  • Large rocks that are used as gravel can be taken out and cleaned separately.
  • On the other hand, the gravel vacuum is the best way to get rid of brown algae on small rocks.

Follow the steps below to vacuum the gravel and get rid of the brown algae:

  1. Put a clean bucket next to the fish tank. The top of the bucket should go right under the aquarium.
  2. Put the whole hose into the water in the aquarium. You can stop water from leaking out of the hose by pressing your thumb down on the end.
  3. Then, pull the end of the hose out of the aquarium and lower it into the bucket.
  4. Take your thumb off the end of the hose so water can start to flow out of the aquarium.
  5. Then, you can hold the cylinder upright and start sucking up the gravel by moving it up and down.
  6. When the gravel starts to move, some of it may come up into the tube. But once the tube is moved, it will fall into place.
  7. Through this process, the brown algae are separated from the gravel. The brown algae will then be easy to clean.
  8. After vacuuming and getting rid of the brown algae, you can fill the aquarium back up with water that is right for your tank.

How To Prevent Brown Algae In Fish Tanks

After you get rid of all the brown algae in your tank, you need to make sure that the environment in your tank isn’t helping it grow back. Even if you get rid of brown algae, it can come back out of nowhere.

These tips can help stop brown algae from coming back.

Ensure Proper Filtration.

A healthy fish tank needs to be set up with good filtration. Check your filter to make sure it can handle the amount of water in your aquarium. Make sure your filter is clean and working well while you’re at it.

Water Flow

Brown algae, called diatoms, can be stopped by moving water. Diatoms have trouble clinging to surfaces in your aquarium if the water is constantly flowing. The extra water flow will also make sure that all of the water in your tank is filtered, not just some of it.

Change Water Regularly

Changing the water in your aquarium should already be a part of how you take care of it. There can be a lot of the nutrients that brown algae likes to eat in tap water and well water. The best water to use is RO water, which has had all of its impurities taken out.

Avoid Over-Feeding.

See how some of the food falls to the bottom of your tank? If that fish food isn’t taken care of, it will go bad and release nutrients that brown algae love.

Stay Away From All Sources of Silicates

If you can help it, you should keep silicates out of your tank altogether because they are thought to play a significant role in causing brown algae blooms. Check the ingredients every time you add something new to your tank. There may be a lot of silicates in your water because of live sand, salt mix, or silica sand.

Why Is There Brown Algae In Fish Tank After Water Change?

If you’ve just completed a water change and noticed a sudden appearance of brown algae in your fish tank, you’re not alone. This is a common problem for many aquarium owners.

Here are the top five reasons why brown algae appear in fish tanks after water changes.

  1. Imbalance in the aquarium’s nutrient levels. When you do a water change, you are removing some of the water along with all of the dissolved nutrients that were present in it. This can cause an imbalance that encourages algae growth.
  1. Too high in dissolved minerals added. This is often the case with tap water that has not been properly treated. The high levels of dissolved minerals can encourage algae growth.
  1. The use of automated aquarium gravel cleaner to do your water changes. It is possible for some dirt and debris to be left behind. This can also lead to brown algae growth, as the debris can provide a food source for the algae.
  1. Changes in the tank’s lighting. If you recently changed the bulbs in your aquarium or moved the location of the tank after water change, this could be causing the algae growth.
  1. Lack of oxygen. This can happen if the water change was not done properly or if there is something blocking the filter intake. If you suspect that a lack of oxygen is causing the algae growth, you should check your filtration system and make sure it is working properly.


Answer FAQ in 2-3 sentences. Use backlinks leading to other articles answering the topic.

Is Brown Algae Bad For Fish?

Brown Algae are a type of algae that can often be found in home aquariums. While brown algae are not harmful to fish, they can cause problems for the aquarium environment. Diatoms can grow quickly and easily outcompete other plants for nutrients, and they can quickly become the dominant form of algae in an aquarium.

How To Get Rid Of Brown Algae In Fish Tank Naturally?

Reducing lighting, lowering or balancing nutrient levels, and maintaining high water quality are all natural methods of controlling and preventing algae in aquariums, while the optimal method for removing algae varies by variety. The presence of aquatic plants and algae-eating fish or crustaceans can also help to control the spread of this unsightly substance.

Why Is There Brown Algae In Fish Tank After Cycling?

It is very typical for new algae growth to appear during the cycling phase. Algae can be gotten rid of in a very short amount of time if the right steps are taken, and there are enough predators to eat them.

How Long Does Brown Algae Last in New Tank?

A tank needs to be “cycled,” or set up with beneficial bacteria and a functioning nitrogen cycle, for roughly four to six weeks. Within that time frame, the brown algae should clear up on its own.

What Temperature Kills Brown Algae?

Diatoms thrive best in cooler water (60-71 degrees Fahrenheit). An increase in temperature would be fatal to them.

What Lighting Kills Brown Diatom Algae?

Diatoms, bacteria, and even some viruses can all be eliminated from water by passing it through an ultraviolet (UV) or ultraviolet (UVC) sterilizer. They are also vulnerable to a bulb emitting light in the red spectrum.


Brown algae in fish tanks can be concerning and frustrating. It is a common problem for both new and experienced fish tank owners. While it is not always easy to get rid of, there are many ways to get rid of algae. With a little bit of effort, you can keep your tank looking clean and healthy. Remember, prevention is always the best cure, so be sure to keep up on those water changes!

Ultimate Betta Fish Care Guide
About the author

Hey! I'm Nicolas from Iguane Media !

Blogger and Owner of the betta care fish guide
Thanks for reading this blog

I'm an Animal Lover


Enjoy this blog? Please spread the word :)