A Guide To Green and Brown Algae in Betta Tanks

Confused about the green floating things in your betta fish tank? Or are they present in all the little nooks and crannies? Should Algae be present in a betta fish tank? Or are you to remove them immediately? We will answer all these questions and more of what you want to know right here. Do not worry, everything seems challenging at the very start. Gear up while we dive into the mysteries of algae, what it is, and what its presence means for your betta fish tank.

Although algae might not prove to be harmful to your betta fish, it looks unappealing in excessive amounts. Join us as we divulge all the secrets to keeping your tank algae-free and how to maintain adequate water conditions.

What is Algae?

Algae is the plural form of the word alga. Algae is an informal name for a large group of plants that are typically aquatic in nature that is they live in or on water. They usually do not produce or bloom flowers and exist in the form of masses. They can be seen in the form of seaweeds and also exist in the form of one-cell (single-celled) organisms. Algae contain chlorophyll and can therefore make their own food through the process of photosynthesis. But lack a proper stem, roots, and leaves. They are the main photosynthetic producers in an aquatic ecosystem.


Algae in your Betta Tank

There are two main types of algae that are commonly found in betta fish tanks that we will be discussing in detail: green algae and brown algae. Although both are present naturally and do not cause any harm to your fish, bettas or otherwise, they are usually undesirable, may look unpleasant to the eye, harm plants, and may indicate underlying harmful water conditions in your betta fish tank. We will be discussing both green algae and brown algae separately in detail, how to avoid their growth, how to remove them from your betta fish tank, etc.

Algae in your Betta Tank

What is Green Algae Anyway?

Green algae are a common sight in your betta fish tank. They have a hair-like, bush-like, or slimy appearance. They take up the Carbon dioxide present in the tank and increase the dissolved oxygen levels by releasing oxygen. But they might take up excess nutrients from the environment leading to an increased level of competition between the green algae and the other plants present in your betta tank. Usually, this leads to the plants suffering.

Green Algae in tank

If the green algae lead to an algal bloom it covers the whole surface of the tank. This leads to a very unhealthy environment since betta fish are jumpers and they breathe oxygen from the surface too.  So an excess of green algae should not be allowed to grow in your tank. Usually, an excess of green algae means underlying bad water conditions. We will discuss all the reasons for excess green algae in your betta fish tank in detail.

Common Causes of Green Algae in your Betta Fish Tank

Although your algae feeder fish would be delighted with all the green algae in your tank, the presence of excessive green algae in your tank may be the result of a number of different factors, which include:


Phosphates and nitrates are green algae’s best friends. They feed on them and require them to grow. When you overfeed your betta fish they do not eat all the food and the excess food sinks down to the bottom of the tank. This discarded fish feed then eventually decays, releasing phosphates and nitrates. Giving the perfect environment for algae to grow. So to limit the growth of green algae in your tank it is important not to overfeed your betta fish.



Green algae are photosynthetic, they, therefore, love the sun, sunlight, and all other forms of bright lighting. They bloom in such conditions and rapidly multiply. If you have an excess of green algae in your tank, you might want to see how much light your betta fish tank is getting.


Betta fish have a natural biorhythm (i.e. circadian rhythm) in which they require about 6 to 8 hours of light daily. Do not light your betta fish tank for more than this time to avoid excessive green algae bloom. If your tank receives direct sunlight, then it is also more likely for green algae to develop and flourish more readily than what would otherwise be seen.

Changing Water Irregularly and Infrequent Cleaning

It is recommended that you change 15% to 25% of the water in your betta fish tank every week or twice a week depending on the size of your tank. This water change helps remove waste products from your tank and prevents green algae from growing. If you see an excessive amount of green algae in your tank, you might want to check when was the last time you changed the water in your tank.

Changing Water Irregularly

The same is the case for cleaning your tank, vacuuming the gravel, etc. removing any waste buildup that encourages green algae growth. It is important to have clean water conditions for the prevention of excessive green algae.

What is Brown Algae?

Brown algae are a form of diatoms that do not require excessive sunlight to grow. They appear to be brown moss and have a furry appearance.

Related Post: Can You Keep A Betta In A Vase?

Common Causes of Brown Algae in your Betta Fish Tank

Some of the conditions that lead to brown algal blooms are similar to what we have discussed above but some are different. We will discuss them here in detail.

Improper Lighting

Brown Algae grow well in dimly lit regions. So it is important you maintain too much light and too little light balance in your tank.

Build up of wastes and nutrients

If your betta fish tank has a build-up of waste materials due to infrequent cleaning, irregular water changes, overfeeding, etc. it makes the perfect conditions for brown algae to grow excessively. So it is important that you avoid such occurrences.


Excessive silicates present in water lead to the growth of brown algae. Silicates and salicylic acid can be present in your tank due to them leaching out of certain decorations and fake plants present in your tank. Or the tap water in your area may contain it. It is important to monitor the silicate level in your tank to avoid brown algae from blooming excessively.

Silicates in fish tank

Improper Aeration

In case your betta fish tank is improperly aerated it can lead to a carbon dioxide (CO2) buildup. Brown algae thrive in a carbon dioxide-rich environment since they take it up and release oxygen. To avoid brown algae from growing in your betta tank it is important for your tank to be properly aerated.

Removing Brown and Green Algae from your Betta Fish Tank

You can remove algae from your betta fish tank in several ways. Some of these include:

  • Cleaning your Tank Manually: You can remove and scrape off the algae present in your tank by hand. They tend to come off fairly easily. But to fully remove them from your tank is it important to get them out of all the nooks and crevices. For this, you might want to remove your decorations and fake plants from the tank and wash them using hot water and bleach. This will kill and remove any algae present there. Bleach is to be avoided on any live decorations and plants, instead simply thoroughly clean them using water.
  • Cleaning the Sand: To clean the sand present at the bottom of your tank you can use a fine sieve or a fish net. You pass the sand through it and any algae or other contaminants present in it are left behind.
  • Cleaning the Gravel: The gravel present at the base of your betta fish tank is also to be cleaned thoroughly. The go-to way to do this is by vacuuming. When you vacuum the gravel any brown or green algae present are sucked up leaving your tank clean.
  • UV sterilizer: An ultraviolet light sterilizer might be a good addition to your tank since it is designed to kill bacteria and algae present in your tank while it does not harm anything else like your betta fish, live plants, or any other fish.
  • Algae Eater Fish: There is many fish that eat the algae that grow in your tank. Instead of cleaning out the algae, you might want to introduce them to your betta fish tank instead. Some of these that are friendly towards betta fish too, include twig catfish, nerite snail, cherry shrimp, plecos catfish, etc.
  • Algaecides and other Chemicals: Algaecides are a form of pesticide that kill algae. If nothing works for you, you can add these to your betta fish tank but this should only be when you have exhausted all other options and nothing else seems to be working. Since they tend to harm the live plants in your tank. Other chemicals are seemingly discouraged but can be used as a last resort. NO3:PO4-X is a similar chemical that helps beneficial bacteria grow which kills off the algae.
  • Filters: Filters exist which can remove phosphates and silicates from your betta fish tank water. They can be installed in your tank. And since brown and green algae require these to grow, their absence will be a great setback to their development.

Preventing the Growth of Brown and Green Algae in your Betta Fish Tank

To prevent the growth of brown and green algae in your betta fish tank the following measures should be adopted:

  • Do not overfeed your betta fish
  • Do not overcrowd your betta fish tank
  • Use algae eaters as your betta fish tank mated
  • Regularly change the water in your tank
  • Monitor the water conditions
  • Do not let the waste material build-up
  • Do not let excessive phosphates be present in your betta fish tank
  • Do not let excessive silicates and salicylic acid be present in your betta fish tank
  • Make sure the lighting of your betta fish tank is proper. Not too much, not too little.
  • Avoid keeping your betta fish tank in direct sunlight.
  • Avoid decorations that contain silica.
  • Clean your tank frequently
  • Make sure your betta fish tank has appropriate filters
  • Keep the water moving by using aerators
  • Make sure your tank has appropriate dissolved oxygen levels and there is no excessive carbon dioxide buildup
  • Add a UV sterilizer to your betta fish tank
  • Vacuum the gravel in your tank regularly
  • Filter and sieve the sand present at the bottom of your betta fish tank
  • Do not leave your tank unattended for extended periods of time

The Bottom Line On Green and Brown Algae In Betta Tanks

Algae in an appropriate amount contribute beneficially to your betta fish tank ecosystem. Taking up carbon dioxide and increasing the dissolved oxygen levels in the tank. In addition to this, it may also be eaten by your betta in some amounts and by your betta tank mates that are algae eaters. So there is no reason to worry about algae being present in your tanks in small amounts. But in larger amounts, they indicate inadequate tank conditions and may prove to be harmful to any live plants growing in your tank since they take up too much of the nutrients present. An excess also looks unappealing to the eye. We have discussed in detail the various measures and practices you can adopt to avoid the presence of algae in your betta tank. We hope they work out for you. See you next time with another article to help you out in your betta-keeping journey. Until next time, happy fishkeeping!

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