Are Hair Algae Bad? (For Fish, Shrimp, Plants & Corals)

Disclosure: When you purchase something through my affiliate links, I earn a small commission. As an Amazon Associate, I earn from qualifying purchases.

It is quite common to find hair algae in aquariums that already house fish, shrimp, plants, and corals. I have encountered this problem countless times in the past.

However, this immediately raises one question. Are this algae bad for these living things? Can they really die from high amounts of algae?

In this article, I will discuss the relationship that hair algae have with these creatures, and whether you should be concerned about the presence of this nuisance in your tank.

Hair algae floating in saltwater.

Are Hair Algae Bad For Fish?

Yes, hair algae are bad for fish. However, they are not toxic.

Donald M. Anderson, Gustaaf M Hallegraeff, and Allan D Cembella released a paper that raised the alarm about the threat harmful algal blooms pose to coastal regions around the world.[1]

They observed that many algae species released compounds that were not strictly toxic. However, those compounds could harm and even kill fish in captivity.

But before you panic, you should look at this other paper from the North Carolina State University College of Veterinary Medicine.[2]

The paper has listed many of the toxic algae that kill fish in a table. First, the author admits that the exact toxins from these algae that kill fish are unclear. 

Secondly, you won’t find the common hair algae species that plague conventional aquariums in that table.

Therefore, you shouldn’t expect the hair algae in your tank to poison your fish. If anything, algae is a sign of a healthy tank.

Some people use the organism to combat nitrogenous waste because it consumes ammonia, nitrites, and nitrates.

However, that doesn’t mean hair algae is harmless. Take the following factors into account:

1. Reduction In Fish Mobility

Hair algae are called so for a reason. They have long strands that can entangle smaller, weaker fish.

A heavy hair algae infestation will complicate movement in the tank. Additionally, entangled fish may starve to death.

2. Oxygen Consumption

People use plants to improve the oxygen content in their tanks. This is because plants take in CO2 and release oxygen.

Unfortunately, plants can also cause oxygen deficiencies by absorbing oxygen and producing CO2. This happens in the dark.

Algae are similar. If you have insufficient lighting, a thriving hair algae population will consume the oxygen in the water, suffocating the fish.

Even if you have a decent lighting system, hair algae can block a plant’s ability to access light, whether it is natural or artificial.

If plants can’t access light, they will steal oxygen from the water, making a bad situation even worse.

Plants and algae both consume oxygen during the day.

3. Destroying Hiding Spots

Like other forms of algae, hair algae are a threat to plants. This makes them a threat to fish because aquatic creatures thrive in planted tanks.

They need abundant foliage to feel safe. If hair algae destroy your plants, the stress may hurt the fish.

4. Clogged Equipment

Hair algae can clog your equipment. This can have a significant impact on the conditions in your water.

For instance, ammonia levels may spike because the filter can no longer control the nitrogenous waste. Your fish will suffer in the long run.

5. Unhealthy Environment

Algae thrive in poorly maintained tanks with harsh lighting, insufficient carbon dioxide, and dangerous quantities of nitrogenous waste.

In other words, an environment that encourages algae growth is dangerous to fish. The fish will die even as the algae multiply.

Are Hair Algae Bad For Shrimp?

Algae’s relationship to shrimp is fascinating. On the one hand, shrimp are scavengers. They will eat anything and everything they encounter in the tank.

Amano shrimp are a famous example. They love soft algae. They have no qualms about eating hair algae, and they are not unique in that regard.

A study in the Journal of Biotechnology (Senthil Nagappan, Shoyen Khan, Mohammad Abdul Qadir, Chandan Mahata, Ann Kristin Vatland) analyzed the viability of microalgae as a food item in aquaculture.[3]

The study noticed that post-larvae Pacific white shrimp had a 30 percent higher weight gain when exposed to a diet constituting moderate concentrations of microalgae. 

In other words, it isn’t a simple matter of shrimp having an appetite for algae. Algae is good for shrimp.

Amano shrimp are among the best algae eaters in home aquariums.

This is also true for fish. However, fish are tricky because some fish species eat algae while others ignore it. You rarely see that sort of discrimination in shrimp. 

Yes, you have dangerous species like blue-green algae that experts associate with neurotoxins and dermatoxins.[4]

A paper in Aquaculture (R Alonso-Rodriguez, F Paez-Osuna) looked at the impact of HABs (Harmful Algal Blooms) on shrimp ponds.[5]

From their analysis, they observed that algae groups such as cyanobacteria had a negative impact on shrimp mortality and growth.

However, as alarming as that sounds, shrimp can survive in a tank with hair algae. Hair algae are not toxic like cyanobacteria.

The shrimp may even thrive in an aquatic space with hair algae. That being said, you have some of the same challenges that emerge in fish tanks.

First of all, the organisms may cause oxygen deficiencies by blocking access to light. The algae can also take oxygen from the water if the light is insufficient.

Like fish, shrimp can become entangled in the algae. They won’t starve because they eat algae. However, the stress will harm them in the long run. 

Algae are less of a threat to shrimp because people use shrimp to control hair algae infestations. This speaks volumes about a shrimp’s appetite for hair algae. 

But they can still die if their aquarium has more algae than they can consume. The conditions in the water will deteriorate rapidly.

Are Hair Algae Bad For Plants?

Aquatic plants require various nutrients to grow and thrive, including nitrogen, phosphorous, and potassium.[6] They also need light for photosynthesis to occur. 

They use light to make carbohydrates.[7] You can find most of these ingredients in a well-maintained aquarium.

Unfortunately, a tank that supports plants is also conducive to algae growth. A combination of light and nutrients will encourage hair algae to manifest.

For that reason, plants are the first victim of a heavy hair algal bloom. 

Because plants and algae use the same tools for fuel, they cannot co-exist in an aquarium. They will compete for nutrients, and the loser will die.

If the tank is poorly maintained, hair algae will come out on top because it will suck all the nutrients out of the water. 

If that isn’t enough, the algae will cover the plants, suffocating them by blocking the sunlight.

Therefore, when hair algae appear in an aquarium, the aquarist’s first concern is the foliage. Hair algae are not toxic to aquatic creatures. 

So long as the parameters are correct and the concentration of nitrogenous waste is low, fish, shrimp, and algae can co-exist peacefully.

Things only take a turn for the worst when the plants suffer. If the plants die, stress will plague the fish and shrimp. The opposite is also true.

If the plants are thriving, the fish and shrimp will recover even as the hair algae fade because they don’t have enough nutrients in the water to sustain their existence.

Anti-algae campaigns can do more harm than good to plants if newcomers execute them carelessly. 

After all, if hair algae thrive in the presence of light, an amateur may respond by keeping the aquarium in darkness for days, possibly weeks, hoping to starve the algae.

If hair algae grow in environments with low CO2 levels, a beginner may saturate the tank with carbon dioxide, unaware of the destructive consequences it can have on fish. 

What about fertilizers? If hair algae consume ammonia, the layperson may ban fertilizers from the aquarium in a misguided attempt to prevent ammonia spikes

That is even though their plants require fertilizers to grow. It takes a careful hand to eliminate the algae without harming the fish and plants.

Hair algae growing on plants may block the light and interrupt photosynthesis.

Are Hair Algae Bad For Corals?

When some people hear ‘Corals,’ they immediately think of ‘Coral Reefs,’ which is a mistake because these two entities couldn’t be more different from one another. 

Coral reefs are diverse marine ecosystems.[8]

Some studies have connected algae to a decline in coral cover, but that doesn’t matter to the average aquarist.[9]

The term ‘Corals’ in relation to aquariums usually refers to tentacled animals that many compare to anemones.

First of all, corals can introduce hair algae to your aquarium. The algae can hitch a ride on the creatures, so careful inspection of corals is essential before buying them.

Hair algae will grow on corals, which is a problem because the algae can starve the creatures. If the infestation is heavy enough, it will block out the light.

Don’t expect the corals to survive this encounter. Additionally, you have all the other concerns aquarists associate with algae, including oxygen deficiencies, dying plants, and deteriorating conditions.

Corals won’t respond well to an aquarium whose ammonia, nitrite, and nitrate levels encourage hair algae growth.

If you find hair algae on your corals, you should test the water for nitrate and ammonia.

So What Should I Do About That Hair Algae?

As you can see, hair algae can harm fish, shrimp, plants, and even corals, especially when they get out of control.

The most decisive factor in the equation is water quality and lack of oxygen. If your tank is full of hair algae, the first step will be to install an air stone.

I personally use the Hygger Aquarium Air Stone (link to Amazon), simply because it is incredibly quiet and handles the water impeccably.

Next, go ahead and remove some of the algae. Here is an article I wrote where I take you step-by-step and explain how to do it.

It is also important to measure the water parameters, as hair algae usually thrive in the presence of ammonia and nitrate.

If the ammonia is above 0 ppm or the nitrate above 20 ppm, you will need to do more frequent water changes and vacuum the substrate weekly.

Pro tip: Algae eaters are a great way to deal with large amounts of hair algae. Here’s a list where I’ve shared the 32 best and worst fish, snails, and shrimp for this job.

If you found this article helpful, these may also interest you:


Hair algae rarely harm living creatures like plants, fish, shrimp, and even corals. However, things change a bit when there is just too much of this algae.

In high amounts, hair algae may block light exposure, which can be a problem with aquarium plants and corals. 

It may also consume too much oxygen, making it a little harder for fish and shrimp. This is especially true in crowded tanks.

Therefore, in some cases, removing some of the algae can alleviate the situation. You can actively do this yourself, or use algae eaters, as mentioned above.