How to get rid of green hair algae

If you’re having problems with green hair algae–you’re not alone. Many of us have struggled with this problem algae in our tanks. It can be a big pain because it can “take over your tank” in a short amount of time. So let’s dive a bit deeper into what causes the problem and how to get rid of green hair algae.

The first thing I want you to do–is to get ready to get frustrated. If you have significant algae growth, this is going to be a pain. I’m sorry for you, in advance. But I don’t want to sugarcoat it. To properly fight green hair algae, you need to fight the war on two fronts–you need to remove the algae itself and find the underlying cause of the problem.

how to get rid of green hair algae
Green hair algae can be quite problematic when it reaches this level of tank domination.

The solution, very likely, won’t be a product you can buy on the shelf of your local fish store, add to the tank, and be on your way. It is very likely that ‘the problem’ isn’t being caused by a single thing. Algae are naturally occurring, and, as you can tell by your own experience, they thrive in the home aquarium setting. But those problems generally don’t arise overnight–they are generally the net result of an accumulation of favorable factors for the algae that tip the balance towards them–and over time, they can become the dominant species in your tank.

To fight this problem and regain control of your tank, your goal is to remove as many of those variables that favor the green hair algae and beat them at their own game (survival and successful growth), tipping the balance back in favor of your more desirable coral species, like coralline algae.

Way # 1: Remove it physically by pulling it out

The first and most important step is that you will literally want to rip the green hair algae off the rocks and out of your tank.  Turn off the pumps (you don’t want to blow filaments around, that will just send them to the far reaches of your tank to grow again), put on a glove, channel your best inner marine iguana spirit (they love eating algae off of rocks in the ocean), get your hand in there and start pulling. You’ll want a slop container with some water in it to collect this mess.

I don’t actually recommend you remove it by mouth. The technique is more like this, literally and emotionally:


The goal here is eradication, so you want to have an eye for perfection and be persistent. Keep up with the grooming over a few days, if necessary–don’t let up.

Way # 2: Turn green hair algae into food

If your local fish store doesn’t have a nice selection of marine iguanas (that was a joke), another option to help get the green hair algae under control is to add some livestock that will eat it. Emerald crabs, Yellow tangs, sea hares, and lawnmower blennies are four animals with a taste for green hair algae. They can help, they are natural, but they probably won’t be enough to get your problem under control.

green hair algae and yellow tang in aquarium with bare bottom
Adding an herbivorous fish like a yellow tang can help put pressure on natural green hair algae populations.

Does anything eat green hair algae?

Luckily, there are several common saltwater fish and invertebrates that will eat green hair algae. A few of the most popular and effective animals are:

  1. Emerald crabs
  2. Yellow tangs
  3. Sea hares
  4. Lawnmower blennies

Way # 3: Treat the underlying issue

At the risk of oversimplifying here, green hair algae need three things to become a pain in your tank.

  1. Nutrients
  2. Lights
  3. Low/moderate water flow

If green hair algae are a new or recent problem in your tank, chances are that something has changed in one of those three categories to make growing in your tank more favorable than it was just a few weeks before.


Nitrates, silicates, and phosphates in your aquarium saltwater can serve as fertilizer, boosting the growth of problem algae like green hair algae. Testing your aquarium water for these pollutants can help you triangulate the problem. In addition to testing your aquarium water, test your source water as well (the water coming out of the tap and the water coming out of your RO/DI unit, if you use one.

Take measures to remove the pollutants with water changes (if nitrates) and media like GFO if phosphates. You can also add macroalgae to a reactor or a sump/refugium to try and outcompete with the green hair algae for nutrients.

Try to figure out what’s causing the spike in nutrients–does your RO/DI need to be replaced? Is your protein skimmer clean and working hard for you? Are you over-feeding your tank? Can you cut back on food waste? It’s probably a good practice to scale back your feeding while fighting this pest, just for good measure.

Are you feeding your blue tang sheets of Nori? Is there a lot of waste? If so, you could cut back on the feedings to only leave what will be consumed in a short period of time.

Nutrient export with a protein skimmer and corals

Another great way to reduce nutrients in your tank is to use a protein skimmer and make sure it is set up properly to pull out dark, foamy skimmate. If you don’t already have a protein skimmer on your tank, you can read about the best models here.

Another way you can reduce the amount of nutrients in the water is by adding more organisms that will actively pull nutrients out of the water for you. Zoanthids, soft corals and macroalgae will help keep those nutrients in check.

Low magnesium in the water

Another possible environmental factor that can tip the scales in favor of hair algae is low magnesium. If your algae bloom is out of control, test the magnesium and supplement if low. You may also want to check the magnesium levels in your reef salt and upgrade if the problem is systemic.

In summary, what you want to do here is get your water parameters within the ideal range, remove the problem, and keep the water within that range.

green hair algae
Emerald crabs like to dine on green hair algae

The spectrum of your lights

How long have you had your current aquarium lights? Over time, the light spectrum that a bulb emits can drift and become more favorable to growing algae. If you have an LED lighting system, changing the mix of blue/white can also have an impact. If you’re having problems with green hair algae, replace the bulbs (if you’re dealing with fluorescents or metal halides) or shift the spectrum of your LEDs towards blue by increasing the blue output and decreasing white. In extreme cases, it may even be worth shutting your lights off totally for a day or two while you physically remove

Water flow

Clean your powerheads/pumps to ensure you’re getting a vigorous flow in your tank. Check to make sure they haven’t moved or recently created dead spots. Consider adding another pump to increase water flow and pressure on the algae.

Are green algae good?

Green algae are harmful in a saltwater aquarium. They can damage corals and starve the tank of oxygen at night when they are metabolically active and not photosynthesizing.

Will green hair algae go away on its own?

Green hair algae will typically not go away on its own. It will grow and spread, making it even more challenging to remove later. It is best to intervene early, with the steps listed here, to help get rid of the problem before it becomes an issue.


Now that you know how to get rid of green hair algae, I hope you don’t want to pull your own hair out. Don’t get too frustrated and lose hope. It’s a battle, but a battle you will win and be persistent.

If you’ve ever battled with green hair algae, please leave a comment here to let us know how you got rid of it. Thanks.


Pick up some extra GFO or bio pellets media here.

For more information about aquarium pests

Check out these other articles about dealing with aquarium pests:

23 Quick tips for controlling aquarium algae

21 Best algae-eating saltwater fish

Fighting brown algae and diatoms

Dealing with cyanobacteria and slime mold

Fighting bubble algae

Bristle worms 

Aiptasia anemone

Go deeper on green hair algae

If you want to dive deeper into this topic, check out this video here:

How to get rid of green hair algae






2 responses to “How to get rid of green hair algae”

  1. James A. Cabeceiras

    Hello only a small problem right now but I think it is the new addition to my lighting? I will turn down the white and add some more blue to the spectrum also add a small yellow tang if I can find 1? I know they were around $35 but because of covid they have jumped up in price to $100! That with the lighting change plus my lawnmower blenny should do the trick. I will keep you all posted! J.C.

    1. JC, sounds like a good plan. Thanks for sharing. I know my Lawnmower Blenny shredded that algae :). Hope yours does the same.

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