Why Does Aquarium Glass Turn Brown? + Ways To Control It

Image of brown algae in an aquarium

Many aquarists work hard to set up a stunning aquarium. However, over time due to negligence, the aquarium can transform into an ugly brown mess. So, why does aquarium glass turn brown?

An aquarium glass turns brown due to brown algae build-up. Brown algae grow due to excess nitrate, silicate, and other nutrients that assist their growth in the water. To eliminate brown algae, change the aquarium water regularly, use a RO filter to lower the silicate, and stop overfeeding the fish.

Let’s now understand in detail what causes brown algae build-up in an aquarium.

5 Main Reasons For Brown Algae Growth In An Aquarium

Brown algae can overgrow and take over the entire aquarium in a short period.

They are capable of turning a beautiful aquarium into an ugly mess.

Given below are the five main reasons for the growth of brown algae in an aquarium:

  1. Exposure to direct sunlight: Direct sunlight can cause brown algae bloom due to increased nutrient levels. Even exposure for a few hours can lead to the formation of large colonies of brown algae. It can be challenging to remove brown algae from the tank, as they tend to stick to the surfaces of glass, rocks, and gravel. They can also clog filters and pumps, deplete water quality, and affect the aquarium’s health.
  2. Poor aquarium lighting: Brown algae are more tolerant to poor lighting conditions. If you use fluorescent bulbs for lighting an aquarium, change them every 9 to 12 months. Poor aquarium light impacts live plants and assist brown algae growth.
  3. Poor maintenance: In the absence of regular water change and poor filter maintenance, the organic debris in the aquarium water will clog the filter. A clogged filter will be unable to clear the waste from the water, leaving a high level of nutrients that are conducive for brown algae growth.
  4. Excess nutrients: Some aquarists feed their aquatic pets more than once or twice a day. Instead of keeping each feeding small, they tend to be too generous. This does more harm than good to the fish since food is left decaying in the water. Also, these excess nutrients will allow brown algae to colonize and expand.
  5. Fish and other waste: Waste produced by fish, decaying plant matter, and decomposing food particles provide additional sources of nutrition for algae. It provides them conditions conducive for their rampant growth.

It’s essential to control brown algae before they spread on the aquarium glass, decorations, and other surfaces making your aquarium look ugly.

So, let’s now understand how to remove brown algae from the fish tank glass.

Recommended Further Reading:

How To Remove Brown Algae From Fish Tank Glass?

Many aquariums, old and new, face brown algae problems.

It’s critical to remove these algae before they take over the tank glass, plants, decorations, and eventually everything in the aquarium.

In the case of a new aquarium, there is no reason to panic. The brown algae will clear on its own within a few weeks.

Moreover, the aquarium fish will also help clear the algae as the algae become more nutritious over time.

However, if your aquarium setup is old, make sure you get rid of the algae as early as possible.

Given below are some ways to remove brown algae from an aquarium:

  • Wipe the glass and other surfaces: Wiping off the algae with a cloth or sponge soaked in warm water will clear the brown algae deposit. You can also use an anti-algae cleaner for this purpose.
  • Use bleach: Soak the decorations in a bleach solution to get rid of the brown algae. However, be careful while using it because too much exposure can be hazardous. Also, rinse all the decorations and aquarium surfaces thoroughly with water to neutralize the bleach.
  • Change water frequently: Changing water frequently will stop brown algae build-up. It will also improve the water quality and prevent further accumulation of algae in the aquarium.
  • Add adequate lighting: Aquarium lighting should be appropriately controlled. Too much or too little lighting can create favorable conditions for brown algae growth. Provide illumination for at least eight hours a day.
  • Use RO filter: Reverse Osmosis (RO) filter is a good option for aquariums. It helps filter large bacteria, lower the silicate content, and create ideal water conditions for the fish and coral. Additionally, it also eliminates toxic chemicals like chlorine and chloramines from the water.
  • Reduce nitrate levels: This is an effective way of controlling brown algae build-up. Place nitrate-absorbing filtrates in the filters. This will reduce the nitrate levels in the tank water and is the best way to remove brown algae deposited on the tank glass and other aquarium equipment.
  • Reduce food waste: Overfeeding the fish contributes to food waste, leading to increased ammonia levels. This encourages algae formation. So avoid overfeeding the fish.
  • Clean the filter media: Clear debris that clogs the filter. Regular cleaning will trap floating waste and decaying matter, allowing proper oxygenated water circulation through the system. In addition, it helps remove harmful substances that can cause brown algae bloom.

Once you remove the unwanted brown algae from the aquarium, you can easily control their growth by following the methods mentioned above.

Now let’s find out if brown algae can go away on their own.

Related Further Reading:

Does Brown Algae Go Away On Their Own?

Brown algae are a form of a diatom.

They are a common sight in a new aquarium setup and form patches on the glass, plants, and decorations.

The primary reason for brown algae growth in a newly set up aquarium is the availability of excess ammonia.

Also, these algae grow because the aquarium lacks a sizeable population of beneficial bacteria required to maintain the balance.

Brown algae can make an aquarium look horrible.

So you must clean the aquarium by wiping the glass, plants, filters, and decorations inside the aquarium.

Moreover, frequent water changes during the first few weeks will help control their growth.

However, once the aquarium has been running for several weeks, brown algae decrease significantly.

Over time, brown algae become more nutritious and get eaten by the aquarium inhabitants.

Proper aquarium maintenance, periodic water change, sufficient oxygenation levels, and constant water circulation will ensure the waste is removed and the plants and other occupants utilize the nutrients in the water.

Once the nitrogen cycle is up and running, there will be a nutrient balance in the aquarium, and the brown algae will eventually go away on their own.

Now let’s see how to control brown algae growth in your fish tank.

Interesting Further Reading:

How To Control Brown Algae Growth On Aquarium Glass?

Brown algae are primarily found in new aquarium setups.

The main reason is the absence of the nitrogen cycle that takes around six to seven weeks to complete and stabilize.

However, they can reemerge in an old aquarium if you fail to maintain proper hygiene in the aquarium.

Given below are some ways to control brown algae growth on aquarium glass and other surfaces:

  • Use high-quality gravel or substrate to provide space for beneficial bacteria. These bacteria help in eliminating fish waste, food waste, and decaying plants and debris.
  • Keep the aquarium temperature between 42°F to 72°F to control brown algae growth. Please note that brown algae prefer cold water to thrive and grow. Warm water will make it difficult for them to survive.
  • Clean all the aquarium parts regularly using a soft brush or cloth. You must remove any fallen plant material from the surface of the aquarium. Fallen leaves and twigs tend to accumulate over time and create ideal conditions for the development of brown algae.
  • Remove any debris lying in the aquarium. Debris accumulates on the sides of the aquarium and provides shelter for unwanted creatures. This creates a perfect breeding ground for brown algae.
  • Avoid adding too much food into the aquarium as it leads to excess bacteria production and build-up of nitrate and phosphate compounds. The excess nutrients that result from this; support the build-up of brown algae.
  • Use Reverse Osmosis (RO) filter to cut down impurities like high levels of nitrate, phosphate, and silicate from the water as they help brown algae growth. However, these filters have fine membranes that remove all the minerals from the water. Therefore, you must replenish the water with calcium, magnesium, and other minerals required by the fish.
  • Clean the filter regularly to avoid clogging. This ensures there is no accumulation of waste products. A clogged filter reduces oxygen levels inside the aquarium and causes stress to the inhabitants. At the same time, it creates a favorable breeding ground for brown algae.
  • Avoid overstocking the aquarium as it increases waste build-up, which may lead to increased ammonia levels. In addition, it results in an unhealthy living environment for the fish and a favorable breeding ground for brown algae.
  • Maintain a stable light intensity by adjusting the lighting according to the aquarium’s needs. Too much or too little light can spur brown algae bloom.
  • Improve surface agitation of the aquarium water. This helps in mixing the water and prevents stagnation which promotes bacterial activity.

With proper care and regular maintenance, it’s possible to prevent the recurrence of brown algae and maintain an aquarium’s stunning look.


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