Sometimes you may wonder, what is this green stuff in my tank that keeps on coming back no matter how much I clean my aquarium!? This persistent green stuff is called algae, and it comes in many different forms, each with its own causes and characteristics.

Algae is a natural part of every aquarium, but when it grows out of control it can become a headache for aquarium owners and fish keepers. If you're seeing green water, fuzzy plants, green or black patches on your decorations and glass, you're likely dealing with algae. Don't worry though! with a little know-how and some simple steps, you can keep algae under control and maintain a healthy, beautiful home for your fish.

 

1. What Is Algae?

Algae are photosynthetic plants that grow in water. They come in various forms, from tiny microscopic organisms to large seaweeds.

In your aquarium, the most common types of algae are green water algae, black beard algae (BBA), string/hair algae, and spot algae.

 

• Green water algae: This algae is also known as an algae bloom, this is when your tank water turns completely green from excessive nutrients and light.

 

• Black Beard Algae (BBA): Dark, bushy strands that grow on plants and surfaces are are normally pretty hard to remove or scrape off with a glass cleaner.

 

• String/hair Algae: Long, stringy, green threads that look like thick lots of green hair attached to plants, ornaments and other surfaces.

 

• Spot Algae: This is probably one of the most common & stubborn algae types, it consists of small, dark green spots often found on aquarium glass and/or decorations.

 

2. Why Does Algae Grow in My Tank?

Algae thrive in aquariums with excess nutrients, particularly from light and organic matter like fish waste and uneaten food. If your tank is receiving too much light, or if you're overfeeding your fish, algae can quickly take over making your aquarium look unpleasant especially if you aquarium has poor filtration and water quality this can massively contribute to algae growth.

 

3. Pro Tips for Controlling Algae Growth

Once you understand why algae appears, it’s time to learn how to manage it. Here are some key tips for controlling algae in your aquarium:

 

Control Light Exposure:
Algae love light, so limiting the amount of time your tank is exposed to light can help prevent it from growing out of control. Keeping your tank out of direct sunlight and aiming for about 8-10 hours of light each day, this can be any time during the day, if you prefer to see your aquarium at night time, you can have it on, just make sure its limited to 8-10 hours to keep the algae at bay.

 

Don’t Overfeed Your Fish:
Excess food left in the tank breaks down into nutrients that feed algae. Only feed your fish what they can consume in about 3-5 minutes, and remove any leftover/uneaten food promptly.

 

Regular Water Changes:
Performing regular water changes (10-50% per week) helps remove excess nutrients and keeps your water clean. This is one of the easiest ways to keep algae under control.

 

Add Live Plants:
Live plants compete with algae for nutrients, which can help reduce algae growth. Adding hardy plants like Java Fern, Anubias, or Amazon Sword can create a more balanced ecosystem and help keep algae in check.

 

Algae-Eating Fish & Invertebrates:
Introducing algae-eating species can help keep your tank clean. Fish like Otocinclus, Siamese Algae Eaters, and certain snails and shrimp love to munch on algae and help maintain a healthy tank. Although these algae eating creatures exist you will still have to clean the aquarium manually! This can be done by keeping the water clean as mentioned previously to help keep the aquarium balanced, even though they may feed on all the algae in your tank these fish still need to be fed algae and/or meat based sinking wafers/pellets for them to thrive they cannot live only on the algae growing in your aquarium!

 

Use Algae Control Products:
If algae has gotten out of hand, you can use algae control treatments. However, be cautious as some treatments may harm other tank inhabitants and can make certain plant species wilt and die off. Please do some research on the products and the plants you are keeping.

 

• Tip: Use these products as a last resort.

 

4. Types of Algae and How to Handle Them

Different types of algae require different approaches. Here’s a quick guide to help you identify and deal with common aquarium algae:

 

Green Water Algae/Algae Bloom:

This type of algae can appear as green water, or as a film on surfaces. It’s usually caused by too much light and/or nutrients such as phosphorus and nitrogen in the water column, this gives a great food source for phytoplankton that cause the water to turn green.

Green Water Alage can also be used for breeding purposes!. This algae has a lot of microgansims floating in the water which makes great food for fish fry!.

 

 

• Solution: Reduce light exposure, especially sunlight, try to avoid direct sunlight as much as possible, do more frequent water changes.

 

Black Beard Algae (BBA): 

BBA appears as dark, bushy patches on surfaces like plants and decorations. It thrives in aquariums with high nutrients and poor water circulation.

 

 

• Solution: Increase water movement, reduce excess nutrients, and manually remove BBA by removing effected plant/plant leaves or by a brush or tweezers. In severe cases you may need to use chemical treatments if necessary.

 

String/hair Algae:

Long, green, and stringy, this algae attaches to surfaces and can be difficult to remove manually.

 

 

• Solution: Reduce light intensity and/or how long your light stays on, improve filtration within your aquarium and add fish that can eat algae. If necessary, you can physically remove string algae by gently pulling it off surfaces with your hands.

 

Spot Algae: 

Small green or brown spots that often appear on glass or decorations. Spot algae can be caused by high phosphates or poor water quality, although this may be the case this algae is completely normal for most aquariums to have form on the tanks glass, its a natural part of the the tanks cycle and just needs a little maintenence to clean off.

 

 

• Solution: Regular cleaning and water changes help control spot algae. Consider using  a cleaning tool such as an algae scraper to easily wipe it off the glass.

 

5. What Happens if Algae Gets Out of Control?

Algae overgrowth can cloud your water, obstruct light from reaching your plants, and make your aquarium look unappealing. In extreme cases it can also harm your fish by depleting oxygen levels or affecting water quality.

 

• Pro Tip: Regular maintenance and addressing algae issues early can prevent these problems from arising.
  
  

6. Establishing a Regular Algae Management Routine

To keep algae under control in the long term we personally think and would advise that its best to establish a weekly routine of regular maintenance, at least once a week.

 

This includes:

 

• Testing Water Quality: Test your water parameters weekly, particularly for phosphates and nitrates, which contribute to algae growth.

 

• Cleaning Surfaces: Use an algae scraper or sponge to clean the glass and decorations regularly.

 

• Trimming Plants: If you have live plants, trim any overgrown leaves to keep them healthy and reduce places where algae can thrive.

 

• Water Changes: Perform regular water changes to reduce nutrient build-up.

 

• Tip: DO NOT USE SOAP, FRESH, OR HOT WATER! it is best to clean dirty ornaments/decorations in a bucket of aquarium water to keep all the good beneficial bacteria that may be attached to them healthy, this bacteria is keeping your aquarium happy and healthy! 

 

• Pro Tip: Using a clean toothbrush works very well for cleaning the more stubborn algae off of rocks and ornaments! 

 

7. Enjoy a Healthy, Balanced Aquarium

By following these steps, you can manage algae in your aquarium and enjoy a healthier, cleaner, and more beautiful underwater environment for your fish, but please know that algae isn't always terrible! even though it may be unpleasant to look at, its a good sign of a happy healthy aquarium!. Some aquarium enthusiasts even prefer the natural look of algae and prefer to keep it in their aquariums. its completely safe to keep and some fish even love to eat it!.

 

• Tip: Remember, algae is a natural part of aquarium life but with a little attention, you can keep it in check and ensure your fish thrive in a balanced ecosystem.

 

• Pro Tip: If you do prefer to keep algae in your aquarium you still need to do regular maintenance such as water changes to keep your aquarium happy and healthy! also by making sure the algae doesn't grow too out of control.

 

 

 

 

CO2 in Aquariums: How to Boost Plant Growth and Fight Algae Effectively

 

Does Adding CO2 Help with Algae?

If you’re wondering whether adding CO2 to your aquarium can help with algae, the short answer is: IT CAN, but only with the right setup. CO2 is especially beneficial for planted tanks and can indirectly help with algae control by promoting healthy plant growth. Here’s how:

 

• Boosts Plant Growth: By adding CO2 to your tank, you provide plants with the carbon they need for photosynthesis. Healthy, thriving plants compete with algae for nutrients like nitrates and phosphates, which can reduce algae growth.

 

• Helps Maintain pH Stability: CO2 helps stabilize the pH in your tank, which benefits both plants and fish. A balanced environment can make it harder for algae to take over.

 

However, CO2 is not a quick fix for algae problems. If your tank has an excess of nutrients (from overfeeding, poor filtration, or other factors such as overdosing fertilisers), CO2 might not solve the issue by itself. It works best when paired with regular water changes, appropriate lighting, and good aquarium maintenance practices!

For more information on adding CO2 and how it benefits planted tanks, check out our How to Boost Plant Growth and Fight Algae Effectively blog!.