Green hair algae | Causes, prevention & algae removal

It might start out innocent enough: a thread here, a tuft there.

And then suddenly… algae explosion! Oops.

The dreaded green hair algae is a notoriously fast grower that can take over your tank in just days. It suffocates your plants, your fish get stuck in it and it looks just plain uglyNo one wants it – but how do you get rid of it?!

Keep reading for everything you need to know about removing (and more importantly: preventing) green hair algae in your aquarium.

Green hair algae: Quick fixes?

Algae is always annoying, but if you have green hair algae in your planted tank you might be especially worried. It blocks the light from reaching your plants and sucks up all those important nutrients. It can be tempting to reach for a quick fix, but unfortunately most do more harm than good.

  • What eats green hair algae? There are plenty of fish and invertebrates that have a taste for algae, but don’t think they can solve your problem. Don’t ever just buy a fish for the purpose of troubleshooting, especially if it doesn’t fit your stock. You are supposed to fix any issues, not your fish.
  • Algae control products? Nope, not the best idea either. Although algaecides might work, they don’t actually solve your algae problem. They just mask it (and might kill all your plants in the process).
  • Scrub, scrub, scrub? Before you whip out the algae scrubber and get to work, keep in mind that removing the algae is just a temporary solution. Although it’s a safer option than algaecides and won’t kill your plants, the problem will just return in a few days or weeks.

So algae eaters, algaecides and simple scrubbing won’t yield the results you’re after. Why?

Because green hair algae is caused by an underlying imbalance. As long as you don’t solve this by adjusting a few important factors in your aquarium, it might disappear temporarily but it will always return.

So what can you do to solve your green hair algae problem once and for all?


Green hair algae: Solutions

Green hair algae in your planted tank has one main cause: Co2 imbalance.

Not nitrate, not phosphate, but Co2. And there are a few easy ways to improve your aquarium conditions that contribute to the (permanent!) eradication of green hair algae.

  • Start working with Co2. Solve the lack of Co2 by adding a Co2 system if you aren’t using one already. I know it’s pricy and can be intimidating, but it’s a great way to balance things out. When done right, added Co2 will help your plants reach their full potential and easily outcompete the green hair algae.
  • Add more Co2. If you already have your Co2 system up and running, it might be a good idea to re-check it. Is it still working correctly? Are you adding enough? If not, up the dosage (making sure it’s still safe for your fish) and you might find your algae problem disappearing or at least lessening within a few weeks. Also be sure to check if your other macro- and micronutrients are present and balanced.
  • Lessen your lighting. Plants use Co2 when the light is on. If your lights are on for long periods, they will use more. If you lessen the amount of light, they will use less Co2 and other nutrients. More Co2 will be available for each plant during the growing time and algae won’t get the chance to take over. 8 hours of light is your max with regular lighting strength. If things are really bad, try cutting your lighting cycle in half. A timer can help if you’re not present to turn the lights on and off at the right times.
  • Liquid carbon. This is another popular “helper” in the battle against green hair algae. It might not be as efficient in supplying your plants with Co2 as pressurized systems, but it does help. More importantly, green hair algae hate it. Dose a product like Easy Carbo daily as recommended, or even apply it directly to the more badly infested areas.
  • Circulation. This is an issue in larger tanks and in set-ups with weaker filter flow. You want fresh water and the Co2 you’re adding to reach every corner of the tank so all plants can benefit. Adjust your filter flow or consider a small powerhead if you suspect there are any dead spots.


The conclusion: green hair algae is caused by a Co2 imbalance. Fix the Co2 imbalance by adding more or decreasing the demand, and you should start seeing improvements over the course of a few weeks. Of course, you can combine this “treatment” with regular scrubbing and algae removal. After all, you don’t want to look at a hairy green tank until the positive changes take their effect!

An important note: If you’ve never worked with pressurized Co2 before, research it thoroughly before you start. Too much Co2 can be fatal to your fish. Also be careful with liquid Co2, especially if you’re choosing to overdose. Although it’s less easy to overdo it, some plants and invertebrates might react badly to it.

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