Hair Algae In Planted Tanks: Causes & Quick Solutions

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Hair algae are a tricky nuisance in planted tanks, as both plants and algae have similar requirements.

This makes it difficult to get rid of the algae while keeping the plants intact. I have personally encountered this problem countless times in the past.

Therefore, to make it easier for you, I decided to collect all the essential information in one article. Let’s dive right into it.

A beautiful picture showing brown hair algae growing on aquarium plants.

What Causes Hair Algae In Planted Tanks?

Most tanks are planted because aquatic creatures use foliage to hide from predators. 

Unfortunately, planted tanks are not immune to hair algae, which can emerge because of one or more of the following factors:

1. There Is Not Enough Carbon Dioxide (CO2)

Carbon dioxide is a complex component. 

A study in Aquaculture (Shazia N. Aslam, Bendik Fyhn Terjesen, Sharada Navada, Vasco C Mota, Gisley R. Bye, Oyvind Mikkelsen) highlighted the threat high CO2 levels pose to fish health.[1]

This other study in the ICES Journal of Marine Science wanted to explore the impact of elevated CO2 levels on the development of large pelagic fish.[2]

Interestingly enough, high carbon dioxide levels did not produce the drastic adverse side effects they expected. 

Nonetheless, most aquarists know that a high CO2 concentration is dangerous to aquatic creatures. But plants are the opposite. 

This paper in ‘Advances In Space Research’ (T. Okayama, T. Takeuchi, Y. Kitaya, K. Murakami) identified aquatic plants as an effective tool for improving water quality because they converted carbon dioxide to oxygen.[3]

Plants play a similar role in aquariums. They consume CO2 and generate oxygen in lit conditions.

Unfortunately, carbon dioxide can also boost algae growth. Low CO2 will inhibit photosynthesis in plants while encouraging hair algae to thrive. 

This paradigm will continue if CO2 levels remain unchanged because the plants cannot outcompete the hair algae for the nutrients in the aquarium. 

Eventually, the plants will die as the hair algae multiply. Low CO2 levels in a tank have numerous sources, but these two are the most prominent:

  • Surface Agitation – Insufficient agitation is bad because it creates oxygen deficiencies. It also lowers the gaseous exchange, preventing CO2 from entering the tank.
  • Excessive Light – Plants use light to consume CO2 and produce oxygen. The more lighting there is in the aquarium, the more the plants will consume carbon dioxide and reduce its concentration.

2. The Nitrate, Nitrite & Ammonia Are Too High

Hair algae thrive in environments with nitrogenous waste and phosphates.[4] The spores prefer ammonia, while the adults consume nitrates.

It takes a strict maintenance routine to keep nitrogenous waste out of a tank because ammonia, nitrites, and nitrates appear when organic matter rots. 

You need a combination of excess lighting, low CO2, and high nutrients to encourage algae growth on a significant scale.

Regarding insufficient surface agitation discussed earlier, it is worth mentioning that it will also cause low oxygen concentrations in your fish tank. 

That is important as nitrifying bacteria will die if you force them to compete with fish and plants for limited oxygen supplies. 

And without nitrifying bacteria, nitrogenous waste will chock the aquarium. 

According to J.I. Prosser (Encyclopedia of Soils in the Environment), nitrifying bacteria use molecular oxygen for respiration.[5]

Many aquarists do not realize that oxygen plays a vital role in nitrifying activities.[6] 

By limiting oxygen levels, you also hinder the work of nitrifying bacteria, which, in turn, benefits hair algae because they consume nitrogenous waste.

3. There Is Too Much Light In Your Tank

As mentioned earlier, excessive lighting can cause algae growth by encouraging plants to consume CO2.

However, light also has a direct effect on algae. Just like plants, hair algae are autotrophs. This means they use light to make their food via photosynthesis.

Many fish owners use lighting to grow their aquatic plants. However, this is a double-edged sword, as it also causes hair algae to bloom on these plants.

Will Hair Algae Kill Plants?

Hair algae can suffocate plants by blocking their access to light and vital nutrients. That typically happens in severe cases with serious hair algae overgrowth.

But plants can also fight back if they have sufficient nutrients. Most commonly, you find some sort of balance between the two.

Does Hair Algae Produce Oxygen?

Hair algae are similar to plants. They absorb CO2 and produce oxygen during photosynthesis.[7] In the absence of light, they do the reverse. 

However, just like plants, hair algae will absorb oxygen and produce CO2 in the dark. In fish tanks, this happens mostly at night.

According to the United States Environmental Protection Agency, heavy algal blooms can cause oxygen deficiencies by consuming too much oxygen and blocking sunlight.[8]

How Do You Get Rid Of Hair Algae In A Planted Tank?

Fighting hair algae in a planted tank is not easy because hair algae utilize some of the same elements that plants require to grow and thrive. 

Therefore, by fighting the algae, you may also harm the plants. Common solutions to hair algae in planted tanks include:

1. Proper Aquarium Maintenance

Quick Instructions:

  • Trim leaves containing hair algae (they will grow back).
  • Make sure the ammonia is at 0 ppm and the nitrate is below 20 ppm.
  • Check if your aquarium filter is clogged on a regular basis.
  • Replace 15 to 20 percent of the water and siphon the substrate weekly.

Maintain your tank to the best of your ability. If you take every step required to create a conducive environment for fish, the hair algae will flee. 

That includes reducing the concentration of nitrogenous waste by performing regular water changes and removing dead organic matter before it decays. 

If you see dead leaves on plants, cut them off. Otherwise, they will become a source of ammonia

You should also trim leaves that hair algae have infested. Some people will remove the entire plant. 

Keeping a toxin-free environment is a crucial step in cleaning a planted tank of hair algae.

2. Increasing Surface Agitation

Use spray bars, wavemakers, power heads, and bubblers to increase surface agitation if the filter is insufficient. 

You can also point canister filters toward the surface to increase agitation. You don’t need any additional tools if the filter is strong enough. 

The filter should turn over the water four times per hour.[9] A strong filter that sufficiently agitates the surface will prevent oxygen deficiencies.

3. Elevating The CO2 Concentration

Quick Instructions:

  • Purchase an airstone and place it in a way the bubbles can reach the surface.
  • Introduce more fish, shrimp, or snails to your tank (increases CO2 naturally).
  • Reduce the lighting (will also be discussed later on).
  • Consider using a pressurized CO2 gas tank or liquid carbon (for experts only).

Algae consume ammonia. However, you don’t fight hair algae by keeping fertilizers out of the tank. 

Your aquatic plants require those fertilizers, especially if the water has a significant hair algae infestation. 

The plants need all the help they can get to compete against the hair algae, which is why CO2 levels are so important.

A high carbon dioxide content allows plants to grow faster, outcompeting hair algae in the process. 

One solution to low CO2 levels is a pressurized CO2 gas tank. This setup includes a diffuser, tubing, a drop checker, and a CO2 regulator:

You can also deploy liquid carbon during spot treatment campaigns, especially when you encounter stubborn hair algae. Aquarists use a pipette to spray leaves with algae.[10]

But you should apply caution. Excess CO2 is dangerous to aquatic creatures. 

Consider this study in the Israeli Journal of Aquaculture (Tetsuzan Benny Ron, Margarita Smirnov, Tamir Ofek), which found that CO2 could be used to immobilize fish permanently.[11]

The study was specifically looking for ways to stun fish before they were processed in a fish plant. In that regard, this side effect of CO2 is a good thing. 

But in an aquarium, you don’t want to saturate the water with CO2. Keep CO2 levels below 32ppm to protect the fish.

Keep an eye out for signs of CO2 toxicity, including loss of appetite and gasping at the surface.

Pro tip: You can estimate the CO2 by measuring the pH and KH in your fish tank. Just search ‘KH pH CO2 chart’ on Google.

4. Limiting The Aquarium Lighting

Quick Instructions:

On average, a typical aquarium requires 8-12 hours of light per day. But if you wish to get rid of algae, eight hours would be the maximum.

Use a timer that automatically turns the lights on and off. Perpetual darkness won’t solve this problem because fish require a few hours of light daily.

Useful Info: Getting rid of hair algae isn’t enough, as they tend to come back. Here is an article where I explained how to prevent this from happening.

What Eats Green Hair Algae in Planted Tanks?

The best solution to hair algae in a planted tank is creatures that eat the hair algae without attacking the plants. Your options include the following:

1. Amano Shrimp (Caridina multidentata)

Tank SetupFreshwater
Care LevelEasy
Minimum Tank Size10 gallons
Temperature60-80° F (15.5-27° C)

Amano shrimp are some of the best tank cleaners on the market. They eat everything, including green hair algae and fish leftovers. 

More importantly, they don’t breed in freshwater. As such, they are unlikely to overrun your aquarium.

2. Pond Snails (Lymnaea stagnalis)

Tank SetupFreshwater
Care LevelEasy
Minimum Tank Size1 gallon
Temperature65-83° F (18-28° C)

Pond snails are incredible. They will make short work of every algae type in your tank, including green-hair algae. 

They stand out because of the ease with which they multiply. You don’t have to breed them deliberately. Once you have one pond snail, more will follow.

3. Siamese Algae Eater (Crossocheilus oblongus)

Tank SetupFreshwater
Care LevelEasy
Minimum Tank Size20 gallons
Temperature75-79°F (23-26°C)

Siamese algae eaters are most efficient when they are young. Their appetite for algae falls as they age. 

But they are peaceful and can be trusted to co-exist with other aquatic creatures.

4. Rubber-Lipped Pleco (Chaetostoma miles)

Tank SetupFreshwater
Care LevelEasy
Minimum Tank Size25 gallons
Temperature72-78°F (22-26°C)

This fish will eat every algae species you can imagine, including black algae and brown diatoms. 

They have a reputation for antagonizing goldfish and eating their slime coat, but only when you fail to feed them.

5. American Flagfish (Jordanella floridae)

Tank SetupFreshwater
Care LevelHard
Minimum Tank Size15 gallons
Temperature64-86° F (18-30° C)

American flagfish are small. They grow to a maximum size of two inches. 

However, they have such a voracious appetite for algae that some aquarists deliberately boost algae growth in their aquariums to keep these creatures happy and well-fed.

6. Nerite Snails (​​Vittina natalensis)

Tank SetupFreshwater
Care LevelEasy
Minimum Tank Size10 gallons
Temperature72–78°F (22–25°C)

Nerite snails are a reliable tank cleaner. They are not only cheap and accessible but also easy to care for. 

They will eat the green hair algae without harming the plants.

7. True Black Molly (Poecilia latipinna)

Tank SetupFreshwater
Care LevelEasy
Minimum Tank Size30 gallons
Temperature70–80°F (21–27°C)

These livebearers are relatively easy to breed. They can also survive in fresh and saltwater environments. True black mollies will scour the aquarium for algae.

Useful info: If you wish to use algae eaters to control the hair algae situation in your tank, here is an article where I listed the best species for this job.

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The best way to combat hair algae in planted tanks is by introducing hair algae eaters, such as Amano Shrimp, Siamese Algae Eaters, Pond Snails, etc.

This is ideal because these creatures will consume the algae while ignoring your aquarium plants. You will not find harder workers than these.

However, there are some things you can do yourself, such as reducing the aquarium lighting and getting rid of nitrogen compounds (nitrate in particular).