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 aquarium” 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 sugar coat 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 factors that are favourable for the algae that tip the balance towards them–and over time, they can become the dominant species in your tank.

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

Step 1: Physical removal


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.

Step 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, and lawnmower blennies are two 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 an aquarium with a bare bottom


ADDING AN HERBIVOROUS FISH LIKE A YELLOW TANG CAN HELP PUT PRESSURE ON NATURAL GREEN HAIR ALGAE POPULATIONS

Looking for other great saltwater fish that eat algae? Check out this article here.

Step 3: Treat the underlying issue


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

  • Nutrients
  • Lights
  • 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 favourable than it was just a few weeks before.

Nutrients


Nitrates, silicates, and phosphates in your aquarium water 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.

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.


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 spectrum of light that a bulb emits can drift and become more favourable 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.

Algae eating fish


Every natural coral reef has its army of algae eaters to keep algae at bay. Algae occur in the wild too, and when a reef overgrows with algae its often a sign of imbalance. If the tank is over four feet in length and 240 litres consider a yellow tang, which will graze rockwork for algae all day long, keeping green hair algae at bay as well as giving itself a feed at the same time. The best of the tangs is the Yellow eye or Kole tang, with specialised teeth to comb and clip hair algae like hair clippers. If tank space allows, a Yellow Tang and a Kole tang can be used in combination to tackle algae, and they live alongside each other in the wild.

Rabbitfish like the Foxface are excellent algae eaters, if a bit large when fully grown, but will help to make short work of green hair algae.

Inverts


If you have hair algae growing everywhere, reach for a Sea hare. These large, brown sea slugs have enormous appetites for hair algae and will make a big difference in just a few days. They are so effective that many are returned to the store after a week or so as they have eaten all the available algae and have nothing more to eat!

To prevent hair algae growth in the first place, reef safe hermit crabs are the order of the day. They will scavenge the rocks all day long looking for all sorts of things to eat from uneaten fish food to various types of algae. Provide spare shells so that they don’t turn on each other or your snail population when they decide to move house.

For stubborn algae consider a Sea urchin. Their tough teeth can even eat rock hard coraline algae, and they will take a thin layer of rockwork off as they graze your reef tank. Make sure your corals are glued down as they have a habit of bulldozing their way through them.

Conclusion


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.

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