What is Brown Algae and The Best Way to Remove it From Your Tank

By Eddie Waithaka @aquariawise

If you are new to the aquarium hobby, there is a chance you are freaking out because a brown-mossy -mess is quickly taking over your tank. I’m equally convinced you are worried this mass might kill your fish, maybe even your plants.

Well, that brown stuff is most likely what many aquarists call brown algae, but botanist correctly identify it as diatoms.

The real brown algae is a distantly related large seaweed as opposed to the microscopic brownish or golden creature hanging out in your aquarium.

And no, it won’t harm your fish, at least not before I help you adequately deal with the problem.

In brief, Low or incorrect lighting from a clapped out aquarium fixture will give brown algae an advantage in any tank, but by far the main boost, especially in new fishtanks, is silicate leaching from a new substrate and aquarium glass or build-up through tap water.

Sometimes even nitrates and phosphates accumulation in poorly maintained tanks.

The easiest way to remove brown algae is by limiting these key factors and physically wiping all surfaces where diatoms have formed.

You can also use silicate absorbing resin in your aquarium filter or stock algae eaters.

There are, however, times when the brown algae will disappear on their own.

To keep the algae from forming altogether, preventative measures like cleaning and changing your aquarium water regularly, plus keeping the water well-circulated should work.

Maintain good lighting as well.

That said, let’s dig into brown algae a little more, we’ll look at:

1. What is and how to identify brown algae
2. What causes brown algae in aquariums
3. How to remove brown algae from fishtank glass, gravel, and plants.
4. How to keep brown algae from coming back

What is and How Do You Identify Brown Algae (Diatoms)?

In science, diatoms refer to a major group of algae, specifically microalgae, that have many genera and species. They are unicellular organisms that are brown to gold in color and have a bony structure that is primarily made of silica nitrates.

Consequently, brown algae thrive in aquariums with high nitrate and silica levels.

The organism at times discharge the silica to form their microscopic home called frustules.

In an aquarium, brown algae will most likely form a golden brown film spreading through the tank and will drab it with what looks like a mess growing inside. The layer classically appear in newly set up tanks usually a few weeks or months after establishment.

But brown algae has no shame, it’ll literally coat everything not just the glass, from the substrate and equipment to live plants and even decorations.

One reason brown algae pose a unique challenge compared to green-algae, is that diatoms will consume silicate. So, while it’s fairly easy to starve normal algae, either by eliminating light or nitrates, brown algae will stubbornly linger in your fish tank.

What Causes Brown Algae in Aquariums?

As I’ve mentioned before, there are a couple of things that contribute to brown algae formation. Majorly silica and nitrate in the aquarium, plus a few other things:

#1— Inadequate Lighting

Brown algae tend to thrive where green algae can’t!

Like in low lights tank where light is not sufficient for green algae to photosynthesis, brown algae will grow. Plus since there are no other algae trying to box them out of nutrients they thrive.

In fact, this is clearly evident in big tanks where the owners purposefully grow algae. In sections of the tank that are properly illuminated, there will be more green algae, with brown algae pushed into the darker crannies of the tank.

#2 — Excess Silicates and Nitrates

Elevated silicates and nitrates contribute to undesirable algae growth, we’ve already established that.

But just how do the silicates end up in your aquarium?

There are a couple of ways, but these two are by far the most probable scenarios:

First, through your water source.

Many water sources contain silicates and silic acid or compounds that contain these elements which eventually breakdown and release the substance into your aquarium.

The second way is through your substrate.

In aquariums where sandy or other forms substrates rich in silicate compounds are used, the mineral leach out and enter your tank quite easily.

Once the mineral builds up to sufficient levels, brown algae start to appear in patches, first on glass or acrylic panes, then covers the rest of the tank. Which usually takes only a few weeks, sometimes much sooner.

This is most likely in aquariums where hobbyists add play or blasting sand to build up their tank. Luckily, sand substrates are not very common in freshwater aquariums.

Whereas you can remove some of the silica from water, you should attempt to keep the level low because you will never remove all the compounds. The recommended levels should be below 0.5ppm.

Then we have your Nitrates!

In a fish tank, rotting leftover food, fish waste and decomposing plant matter produce ammonia, which is harmful to your fish. Therefore, the bacteria in your biofilter convert the ammonia first into nitrites and then nitrates.

Therefore, should you fail to do frequent water changes, the nitrates hang around your aquarium and conveniently feed the brown algae.

Water used to fill the aquarium also often has nitrates in it. In the United States, drinking water may have nitrates as high as 40 ppm.

Levels even as low as 10ppm will sprout the diatoms. Thus, freshwater aquariums should be kept below 5ppm, and preferably below 2.5ppm if you are already battling brown algae.

Also, although nitrates are not directly lethal in the way ammonia and nitrites are, over time, high levels have a negative effect on fish and plants.

#3 — No or Inadequate Filters

Though nitrates remain in your aquarium water, your filter plays an important role in sorting out any excess amounts.

Mechanical filters physically traps particles of uneaten food, fish waste, decayed plant materials, and other debris in your water. This reduces ammonia build-up and consequently lower nitrate level.

There are also filters that’ll remove excess nitrates albeit more expensive compared to other units. Moreover, instead of expensive special filters, combine simple filters with different media to reduce the nitrates. Plus add aquarium plants to use up the nitrates in the place of diatoms

Also, keep in mind many hang-on-back style filters can expose the water to a very large amount of light, depending on the brand and the ambient lighting in your aquarium room.

That said, though you may have adequate filtration, you need water movement as well to discourage diatoms.

The water current will create movement and make sure all the water is filtered plus prevent diatoms from attaching to you aquarium surfaces.

How to Remove Brown Algae

There are a couple of ways to deal with brown algae, some better than others and some last resort. It will also depend on which part of your aquarium the diatoms have formed.

Generally, remove brown algae by:

• Wiping off all aquarium surfaces and vacuuming your substrate. Use a suction remover or your hand to physically remove the accumulated brown algae. This is important since Diatoms left in the tank will spread faster.
• Providing appropriate lighting, making sure the tank gets at least 6 to 8 hours of light in a day. Even so, 6 hours of light are only adequate when you don’t have plants in your aquarium.
• Stock algae eaters like dwarf suckers (Otocinclus), pleco fish (Plecostomus) like bristlenose plecos, or shrimp.
• Use silicate adsorbing resin in filters, as well as clean the filters and change the water regularly to ensure you have quality water that is free from nitrates. Change the water and clean the aquarium at least twice per week.
• Avoid sand substrates especially in new aquariums where silicate is present.
• Check your tap water silicate and nitrate levels before replacement and also consider using filtered water from an RO unit to control the growth of brown algae.

How to Remove Brown Algae from Aquarium Glass

Brown algae are not very strong so wiping them from your aquarium glass should be fairly easy.

Regardless of whether your aquarium surface is glass or acrylic, simply wipe the glass in single smooth wiping motions, making sure very little brown algae debris get in your aquarium while you wipe.

You can either use a small cloth or sponge or you can opt for an algae scraper or squeegee.

The scrapers you user could even be a magnetic aquarium glass cleaner type that doesn’t keep falling off the glass. Something you don’t want when getting rid of brown algae.

How to Remove Brown Algae from Gravel

Removing brown algae from your aquarium gravel substrate or pebbles will depend on the size of your pebbles.

Large rocks can be removed and wiped individually, whereas for smaller pebbles and fine gravel you will need to do some vacuuming.

Aquarium gravel washer or siphon kits are built to effectively separate and remove debris, including brown algae, from aquariums. The kits come in varying sizes and thus will depend on how big your aquarium is.

On average, for about $8 dollars, you will get a basic 10 to 20 gallons aquarium siphon vac kit. Moreover, most of these kits should be fairly easy to use as long as you follow the instruction provided on the gravel washer manual.

When cleaning the gravel, make sure you only clean the top layer to avoid removing beneficial bacteria in your tank. Which could be a catalyst to the brown algae than a remedy.

How to Remove Brown Algae from Sandbed

I should mention that most people with freshwater tanks won’t have sand but use gravel instead. Because sand has a tendency to get kicked up very easily and get into filters which are quite sensitive.

That said, if you have sand in your aquarium and you want to clean it, just use the siphon method same you would with fine gravel.

When your aquarium brown algae problem is major you can choose to do the siphoning cleaning during your weekly water change. This will not only remove the brown algae but all debris in the tank then you don’t have to rely so much on your filtration system.

When vacuuming the sand, first remove all the decoration, this will make sure any sand kicked up doesn’t end up stuck on the decoration.

How to Use a Siphon Vac to Remove Brown Algae from Your Aquarium Gravel or Sand

1. Place a clean bucket near your aquarium and be sure the top of the bucket is below the bottom of the aquarium. Also, make sure you use a bucket that has been selected for your tank maintenance only. Using a bucket that has had a cleaning solution or soap in it can be fatal to your fish.
2. Submerge the entire hose and tube into the aquarium water. Then manipulate the kit so that all air escape and the entire unit fills with water.
3. Hold your thumb tightly over the end of the hose so water does not escape. Lift the end of the hose out of the aquarium and lower it into the bucket.
4. Remove your thumb from the end and water will begin to siphon from the aquarium.
5. Immediately hold the cylinder verticle and begin vacuuming the gravel using an up and down motion. Some gravel will rise into the tube but will fall into place once the tube is lifted. The process should allow debris like brown algae to separate from the gravel for easy removal. After you are done with vacuuming, refill your aquarium with water that matches the conditions of your tank.

How to Keep Brown Algae from Forming or Coming Back

Prevention is better than cure and in this case will save you time, money and a whole lot of stress.

So, to stay ahead of brown algae, the first half is knowing what causes the overgrowth and then work to prevent a future overgrowth situation.

Listed below are some of the best ways to prevent brown algae from coming back:

• After removing the algae its imperative to maintain a low nitrate environment. So, change 10 to 15 percent of your aquarium water every once or twice a week. Clean more if the brown algae are becoming a menace.
• If the tap water you’ve been using contains silicates it is necessary to use RO water during water changes. Also, test the water for phosphates and consider using appropriate mineral removers or find another source if need be.
• Improve the light in your aquarium and replace any broken fixtures. Also, consider your aquarium light schedule and use it against the brown algae growth.

Enjoy your aquarium.

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