Hair Algae In Saltwater: Causes, Treatments, Eaters & More

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Hair algae are quite common in freshwater aquariums, but they also grow in saltwater. This ends up raising some questions among aquarists who own a reef tank.

In this article, I will discuss what is unique about hair alga in saltwater tanks, what causes it, how to get rid of it, and what creatures eat it.

So, without further ado, let’s dive right into it.

Hair algae can grow in saltwater just as they can in freshwater.

Can Hair Algae Live In Saltwater?

Yes, hair algae can live in saltwater, which is true for most algae types. However, some reports may seemingly suggest otherwise. 

For instance, biologists from the Monterey Bay Aquarium Research Institute discovered a new group of algae called ‘Rappermonads’ that live in both freshwater and marine environments.[1]

This sounds like a big deal. It suggests that algae do not typically inhabit both freshwater and marine environments.

A US Geological Survey study took things a step further in 2018 when it investigated algae in Lake Okeechobee.[2]

The study found that blue-green algae released toxins when it encountered salt water. The saltwater weakens the cell walls, allowing the toxins to leak. 

This went a long way in justifying the theory that saltwater could kill freshwater cyanobacteria.

However, before you conclude that algae cannot survive in saltwater, consider this Florida Health guide, which identifies blue-green algae (Cyanobacteria) as an organism that lives in freshwater, saltwater, and brackish water.[3]

You should also consult the Centers for Disease Control and Prevention. 

They released an article exploring the dangers of algal blooms in saltwater bodies such as oceans and bays, proving that algae occur naturally in saltwater environments.[4]

What does this mean? Experts at Garden Guides have the answer. They encourage aquarists to kill algae in ponds by adding rock salt.[5]

That doesn’t sound like it tells you anything. However, they have warned aquarists against using too much salt because doing so will kill plants and fish.

In other words, too much salt can kill everything, be it plants, fish, or algae. 

However, hair algae will tolerate the conventional salt content you find in a marine aquarium.

So long as the right ingredients are present, algae will appear, whether you want it or not. It is worth noting that algae are not always bad. 

They absorb toxic elements like nitrates and nitrites. Although, that doesn’t mean you should permit the organism to run amok.

Here you can see the filamentous form of hair algae under a microscope.

What Causes Hair Algae In A Saltwater Tank?

Like every other organism in a saltwater tank, hair algae thrives when you expose it (knowingly or unknowingly) to the right conditions, including:

1. Organic Nitrogen Compounds

Nitrogenous waste is just as problematic to marine tanks as it is to their freshwater counterparts, which is why cycling is so important. 

Without nitrifying bacteria, ammonia will poison your fish. Algae appear during the cycling process because nitrogenous waste is present in significant quantities. 

First, ammonia will spike. Once nitrifying bacteria appear, the ammonia concentration will fall while the nitrites increase. Eventually, the nitrites will also disappear as the nitrate levels rise. 

Like plants, algae use nitrates as food. But they will happily consume ammonia and nitrites as well if that is all you have in the tank. 

You can’t eliminate nitrates from the water because they originate from ammonia, and ammonia is a mainstay in aquariums.

So long as the tank has living fish that eat food and produce waste, ammonia will always appear. This, in turn, means that algae are guaranteed to appear.

2. Inorganic Phosphates

A study in the Journal of Freshwater Ecology (Meng Li, Qiulei Xu, Xianling Xiang, Yuan Li, Yilong Xi, Muhammad S. Iqbal) wanted to investigate the significance of phosphorous in the growth of algae.[6]

It noted that phosphorus was a vital aspect of an ecosystem’s stability, maintaining the growth of organisms in any given aquatic environment.

In that regard, you could argue that phosphates are just as crucial to algae growth as nitrates, and unfortunately, they appear in every aquarium. 

This is good for the other organisms in the water. But it is also bad because it boosts algae growth. 

Algae readily consume inorganic phosphates such as orthophosphate. It only takes a pound of phosphates to support 500 or more pounds of algae.[7]

Some people dismiss phosphates as a potent algae source in saltwater aquariums because their tests detected minimal phosphates in the water. 

They don’t realize that a significant algae population can consume inorganic phosphates as quickly as they enter the water, essentially hiding the high phosphate content you have in the tank.

3. Light (Natural & Artificial)

Excess lighting encourages algae growth, regardless of whether it’s natural or artificial lighting. 

This is why direct sunlight is dangerous. Aquariums positioned next to windows usually struggle with incessant algae blooms.

This is also why you typically see excessive hair algae growth in aquariums that are consistently lit, especially during the night.

Keeping the aquarium lights on at night increases the chance of algae overgrowth.

How Do You Get Rid of Hair Algae In A Saltwater Tank?

You have a multitude of practical solutions at your disposal where hair algae in saltwater tanks are concerned, for instance:

1. Reduce The Lighting As Much As Possible


  • Make sure your tank is not lit for more than 8 to 12 hours a day.
  • Place your tank in a spot that doesn’t get direct sunlight.
  • Reduce the lighting intensity by at least 50%.
  • If you don’t have a dimmer, you can choose less intense lighting or reduce the number of bulbs in your aquarium.

I also suggest doing a little research on how much light your aquarium inhabitants require, and adjusting the lighting accordingly.

Make sure the light is only bright enough to view the tank’s inhabitants. The brightness of the light is just as important as the duration. 

2. Commercial Algaecides (Not Recommended)

To be honest, I have never tried commercial anti-algae products before. It’s just because I’ve heard bad things about them. 

Some of my aquarist friends said they didn’t work, while others said their fish started swimming and acting oddly after using them.

But commercial products are sometimes the first solutions newcomers reach for because they are easy to use and they deliver relatively quick results. The dosage is crucial. 

Experts from the University of Florida commended copper as a potent means of fighting algae in marine aquarium systems.[8]

However, they also warned that high copper concentrations could kill fish, harming the gills and depressing their immune system. Pay close attention to the instructions. 

If you have doubts, move the fish to a separate tank while you treat the main aquarium with a copper-based algaecide. 

3. Clean Your Tank Regularly


  • Perform weekly water changes of 15 to 20 percent.
  • Vacuum the substrate once a week.
  • Avoid cleaning the filter media too thoroughly. Large debris can be removed from it, but do not wash it under tap water.

Start by keeping the tank clean. Perform weekly water changes to keep ammonia, nitrite, and nitrate levels low

You may also consider investing in a reverse osmosis system that purifies tap water before you add it to the aquarium during a water change.

Reverse osmosis will remove every toxin that threatens your aquarium, including phosphates, nitrates, and chlorine. 

You can also buy filter media and sponges that absorb nitrates and phosphates, such as the API ZORB Filtration media (link to Amazon)

It is essential to vacuum the aquarium substrate at least once a week to avoid ammonia, nitrate, and algae.

4. Change Your Feeding Routine


  • Feed your fish the amount they consume within two to three minutes.
  • Manually remove leftovers seen on plants and decorations.
  • Siphon the substrate on a regular basis.
  • Don’t feed your fish simply because they seem hungry.

Avoid overfeeding your fish at all costs. Overfeeding increases the quantity of waste and leftovers.

The more waste and leftovers you have, the higher the ammonia concentration and the more nitrates you will record in the long run.

You may also invest in an automatic feeder to ensure the fish get the same amount of food daily.

5. Remove The Algae Manually


  • Pick a toothbrush and tangle the hair algae with its shaft. 
  • Turn the toothbrush and pull as much hair algae as possible. 
  • Pull the toothbrush out and collect what remains in the container manually. 
  • Siphon the substrate to remove the residue.

It is perfectly normal to remove hair algae manually, both in freshwater and saltwater tanks. Just make sure to wear gloves before starting.

If all that sounds confusing, here is a video showing how to do that:

Pro tip: Removing 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 Will Eat Hair Algae In A Saltwater Tank?

You don’t have to deploy risky algae removers such as copper-based algaecides when you have algae eaters like the following:

1. Tuxedo Urchins (Mespilia globulus)

Care LevelEasy
Minimum Tank Size30 gallons
Temperature72-78° F (22-26° C)

Urchins love hair algae. They can eat them all day and all night. Look for the tuxedo sea urchin in your local store. 

People often overlook this creature whenever they discuss aquatic cleaners. 

They obsess over shrimp and snails because they are unaware of the love these creatures have for algae.

The herbivores will leave scrape marks on surfaces like rocks as they graze on the algae. You will see them roaming the aquarium after dark in search of food. 

2. Sea Hares (Anaspidea)

Care LevelModerate
Minimum Tank Size20 gallons
Temperature73-81° F (23-27° C)

These nocturnal creatures have two tentacles that look like rabbit ears, hence the name.

Aquarists with reef aquariums use them as algae cleaners because they can eat most algae types. However, they also eat plants. Keep that in mind. 

3. Tang Fish (Acanthurus achilles)

Care LevelModerate
Minimum Tank Size100 gallons
Temperature72-78° F (22-26° C)

Tang fish are saltwater herbivores that love green and brown algae. They will remove algae from the rocks and walls of the aquarium. 

If you have a severe hair algae infestation, stop feeding them for a little while. This will encourage the fish to eat the hair algae.

4. Gobies (Gobiidae)

Care LevelModerate
Minimum Tank Size20 gallons
Temperature74-80° F (23-27° C)

Gobies love algae. Hair algae are the court jester goby’s primary source of nutrition. The hector goby’s appetite for algae is equally large. 

These creatures will rummage through the substrate in search of detritus, which makes them great tank cleaners.[9]

They also have a peaceful temperament that allows them to co-exist with other friendly fish.

5. Coral Banded Shrimp (Stenopus hispidus)

Care LevelEasy
Minimum Tank Size30 gallons
Temperature72-78° F (22-26° C)

This creature is beautiful. However, it manifests aggressive tendencies when paired with other shrimp.

Therefore, you should only keep one of these creatures in your tank at a given time.

The only exception is when you want to breed them; in this case, a mated pair can inhabit the same marine environment.

Coral-banded shrimp are decent tank cleaners that eat algae, detritus, and parasites. They can grow to a size of 3 inches.

Pro tip: Here is my complete list of hair algae eaters. You will find plenty of saltwater fish, shrimp, and snails that eat hair algae vigorously.

If you have these algae eaters in your aquarium, but they have shown no interest in the hair algae, you should reassess your situation. 

Are you sure you have hair algae? Some people confuse strings of bacteria for hair algae.[10]

If you have an omnivore that eats algae, it may ignore the hair algae if you provide plenty of food from the outside.

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Hair algae grown in reef tanks are not much different than those grown in freshwater tanks. The causes are the same, as well as the way to get rid of them. 

Naturally, the creatures that are able to eat these algae will be different. However, you can still find plenty of fish, shrimp, and snails to help you fight the nuisance.