My tank has hair algae – how do I get rid of it?

Does this picture look familiar?

Don’t you just hate this stuff?!

I can almost guarantee that you will have probably seen this at some point in your aquarium. It’s a frustrating algae because it looks awful and can be hard to get rid of. But don’t panic, as I can solve your situation. PHEW! *wipes brow*

Let me first sort out an old wives tale and set some of you straight:

It has nothing to do with excess nitrates or phosphates

Now I’d like to quote some text from UKAPS which is an excellent forum for those who do not know. Clive, who writes a lot on there has a real knack for words and I just love what he wrote:

Hair algae has absolutely nothing to do with high NO3 or high PO4. Hair algae is strictly associated with poor CO2. My tanks always have super high NO3 and PO4 and they never get hair algae – until something goes wrong with my CO2.

Just because you are adding CO2 it does not mean that you are adding enough. Do not fall off the wagon. Do not look for other reasons. Only try to realize the truth. Moss is a low light plant, so when you pummel it with high light it suffers more than other plants if the CO2 is not excellent. Therefore the moss is telling you that it is suffering too much light and not enough CO2. You think your CO2 is good but your moss disagrees. At the end of the day it doesn’t matter what you think, it only matters what your moss thinks.

Step number 1 is to reduce you lighting intensity significantly by 50% if possible. This will reduce the environmental pressures on the moss.

You also need to increase your CO2 levels without killing your fish. If this cannot be accomplished by gas injection rate increase then you need to add more liquid carbon and this has to be done daily, not once or twice a week. The liquid carbon is hostile to CO2 related algae and at the same time it delivers CO2 to the plant. You can use the bottle recommended daily dosage or you can multiply that by 2X or 3X assuming that you don’t have plants that respond poorly to liquid carbon such as Riccia or liverworts/bladderworts or assuming that you don’t have fauna that are sensitive to liquid carbon such as some shrimp.

Increase you number of water changes per week for a few weeks if this is possible.

As you lower the growth demand via reduction of the light intensity, and at the same time improve the available CO2, you’ll find that the mosses and other plants will respond positively and will grow faster. The hair algae will subside. Use a toothbrush in a spiral motion to remove as much of the hair as you can.

This advice is soooo good and so honest. Let me know what you think. Have you suffered from hair algae or maybe you are suffering right now from it. Either way, let me know!

42 thoughts on “My tank has hair algae – how do I get rid of it?”

  1. Richard, I read the article on hair Algae on Moss which I have in my 125 Ltr Tank. To reduce the light intensity what would be best ,my lights are on 8hrs 3 in a morning 5 evening I also have Two Reflectors, should I remove the reflectors leave the lights at 8hrs or drop to 6hrs leave the reflectors where they are.
    I dose 5ml daily with Aqua Nourish and 2.5ml daily with Aqua Carbon would it be beneficial to increase the Carbon or leave that as it is.

  2. Yes remove the reflectors for the moment if you want to keep the lights on for 8 hours. However from an economical point of view, keep them on and run lighting for only 6 hours (cheaper).

    I would also increase your Nourish to 7-8ml and 5ml Aqua Carbon. This will help.

    Please keep me posted as to how your tank develops.


  3. Hi Richard, just an update on the progress of getting rid of the Algae on the moss in my tank. Have left reflectors on and dropped the lighting to 6hrs without a break and upped the ferts and carbon as you suggested, done this gradually,at first I seemed to get hair algae on other plants thought I might have done the wrong thing but over time that has reduced down to hardly any. The moss has had a good trim and it has improved, with the extra ferts all the plants are looking good so Thank You once again for your help.


  4. Hi Richard

    I inject Co2 into my tank (250L) which is on a timmer and starts injecting into the tank 2 hours before the lights come on. I have a drop checker installed to measure Co2 and my lights are on for only 6 hours.

    Question: At what point, when your lights come on, should the color of your drop checker be?

    At present when my lights come on, the drop checker shows blue and by the time the lights go out it will be lime green. Is this right?


    David James

    1. In an ideal world David, when your lights come on, your drop checker should be green (or nearly green). This would mean your plants have the perfect CO2 levels so they can literally start growing straight away.

      So you either need to have your CO2 to come on earlier or your CO2 levels are too low in the first place (I suspect the latter). In most cases if you have your CO2 levels set up right, 1 hour should be sufficient to get your CO2 to the right level for optimum photosynthesis.

      A few questions for you:

      How many bubbles per minute are you running your system at?

      Where in your tank is the location of your drop checker?

      Are you using a secondary circulation pump to move your CO2 around the tank?


  5. HI richard – I have recently had a large growth of this hair algea in a 260L tropical community tank – I haven’t got any real plants but only plastic ones . I have already reduced the lights from 8-6 hrs but so far no change – any thouights would be gratefully recieved ..yours Fritz

  6. Hi Dr Richard,

    I read your article on hair algae and I tried some of the method but the hair algae seems to be growing strong.

    I have an odd size tank, 36″ x 5″ x 12″ (wall mount tank). I am on pressurized co2 (2-3 bps) I have been dosing Seachem Phosphorus, Nitrogen, Potassium and Comprehensive and daily supplement of excel, EI method and does weekly water change.

    My plants are HC, fissidens, anubias nana petite and hair grass. I have reduced my lighting to 5 hours a day, co2 is on 1hr before lights on. However, the hair algae situation did not improve. I see most of my plants pearl around my tank.

    I read on your article to increase water change, do I need to continue to add fertilizers after each water change? Currently dosing NPK on and Comprehensive on alternate days.

    I feel like I’m fighting a losing battle. What should my next step be?
    1. Continue the 5hours period and reduce the intensity?
    2. Do 2 time water change per week?
    3. Blackout for three days?

    Any suggestions will be greatly appreciated.


    1. Are you using a drop checker with bromo blue?

      Is your CO2 up to scratch (i.e. is your drop checker green when the lights come on?)

      Which plants are suffering from hair algae? All or just some?

      Increase water change (40% 3 times a week in this case) and then re-dose fertilisers each water change

      Reduce lighting intensity, increase fertiliser dosage, increase water change = no algae

      1. I’m not using drop checker as I couldn’t get my hand on 4kh solution and if I use the tap water, it always yellow but the fishes show no sign of lack of o2.

        It started with Fissidens and now it has spread to HC, some rocks and Anubias and hair grass, basically everywhere now. It not as bad as it sounds, it just a few here and there but growing worst.

        I will try out the 3 x water changes and reduce the intensity of the light.

        Thanks for the advice, will update in a week’s time of the progress.

        In the meantime, if you have any other solution that you feel I should give it a shot, do let me know.


        1. If you’re not using a drop checker, you may as well just put your finger in the air and try and guess wind speed. It’s as simple as that.

          If you want to stop your algae from growing, buy a drop checker and bromo blue – both sold on our site. This will help you enormously and I look forward to your update.

          How about showing a picture too?

          1. Finally got the drop checker sorted out and you are right!

            It was not even green based on my last co2 configuration. I increased the co2 significantly (almost doubled the previous amount) and its very light green near to yellow at the end of the 5 hour light period.

            I increase the intensive of the lighting to normal and I noticed crazy pearling of all the plants at all areas, except one area which I will check the flow.

            Will observe if the hair algae situation improves over the next few days.

  7. Hi dr. R, great thread. Been following the tips for over 2 weeks now,…. And really happy to say it is working! My next step is to add a load of amano shrimp to clear up the remaining hair algea, but my question is when / how should I start stepping the lighting back up? Ie. should I do this by going up 10% a week, etc?

  8. I have a 125 L tank with live plants and fish. I have had black hair algae which seems to like growing on the edges of the leaves ( Echinodorus sp, Vallisneria and Anubia, and also on the bogwood. When the leaves become very infested I have been chopping them off – not sure I should be doing this? I have just read the post about increasing CO2, decreasing light and upping the fertilizer. I currently use Flourish Excel Liquid Carbon – 2.5ml daily and Flourish plant supplement fertilizer – 2.5 ml twice a week. I have started to do 2 partial water changes a week. After reading your article it seems I can :
    * double the liquid carbon to 5ml(I dont have the gas injection system),
    * increase the fertilizer – Im not sure how much I can increase it to and how often as bottle says twice weekly. Can you advise for this brand of Fertilizer please?
    * decrease the time the lights are on from 8 hrs to 6 hrs. Will this be enough lighting for my plants though – I thought they needed more light than this to do well?

    Sorry for all the questions but this is a new hobby (which I love). I Just want to be sure this is safe for the fish and if the plants will lose the algae over time or if I will still need to remove them and buy new ones.

    Hope yo can help, thanks so much


      1. Thanks Dr R,

        I have ordered the fertilizer (and also some liquid carbon of the same brand) that you have suggeted so will see how it goes. Will let you know if Im successful in ridding my tank of the hair algae……

  9. Hello Richard,

    Just wanted to let you know that my tank is looking great, Hardly any hair algae. I am using 5ml Neutro T fert and 5ml of Nertro T liq CO2 daily as you suggested and I have my lights on a timer so they only come on for 6 hours a day at the moment. This really seems to have worked – Plants are looking good – healthy and nearly algae-less and fish v happy – and me 🙂

    Thank you

  10. Hi Richard, My shrimp tank is infested with hair algae and so far all I’ve been doing is removing it by using a toothbrush but it’s a losing battle. Can I use CO2 with CRS,CBS, Babaulti, Blue Bolts and TB’s ? It’s only a small tank, 23 litres, so how much would I use if I can use it at all? Thanks for your advice. Helen

    1. Sure you can and don’t be scared of CO2. It’s really easy and helps so much too. You’ll need a CO2 set like this one

      the great thing about this set is you can use a solenoid with it so you don’t waste gas

      and then the icing on the cake is using this adaptor allows you to use this big 800g bottle

      To monitor your CO2 use this

  11. So I have a hair algae EXPLOSION in my tank in my moss on the wood. I panicked and cut all nutrients and liquid c02 in the tank. Today I reduced my lighting hours, should I start dosing co2 again then? Really need to get this spurted as my moss is dying 🙁 Thanks

  12. I’ve got a 240L heavily planted tank, run the lights on a six hour cycle, and the co2 an hour before lights on then off an hour before. I do a weekly 25% water change, I dose with ferts weekly too. My Co2 circulation is fine, my drop checkers all indicate a light greeny yellow. And with 2 externals and 2 internal power heads, I think my Co2 distribution is pretty good.

    My question is, can light intensity further promote hair algae grown. I suspend my 2 Kessil A150s about 7′ from the surface of the water, my tank is also quite shallow at 45cm. I also have some black algae on a handful of plants. Is that indicative of another underlying issue?

  13. I have a Shrimp tanks with Java and Christmas moss. I had to change 2 tanks due to green hair algae. even in new tanks it has started spreading fast.. Im sick and tired with them green hair algae.

    Tank Conditions;
    Tank Size: 90cm x 30cm x 35cm
    Water – Changing 25% – 35% water every week
    Light – 0.5 W LED strip ( 20 LEDs) daily 10 hours.
    water pump: 200 liters per hour
    CO2 – Not Given
    Plants: Vallisneria, Java Moss, Christmas moss, crypto, HM

  14. Just Read every bit of blog on here and now I’m asking have you seen Algexit made by Easy Life cost £7.20 250ml treated tank now waiting for things to happen NOT things got worse could have poured Bottle in useless so cut lighting and dosing liquid CO2 going to feed daily and up the anti on water change if this fails il go Plastic

  15. Hi. I am really new to fish ownership. I have brow hair algae in my cold water tank, I haven’t any real plants and was unsure if the advice about the liquid carbon and light was the same

    Thank you


  16. Wow thank you for the write-up! I’m new to a Planted Co2 Aquarium and have recently got this problem . I will take all the advice given, eg: more water changes, manually removing hair algae, upping the Co2, I cannot lower the lighting but I can reduce the times. It comes on at 12-9pm. I donot use ferts or have a dirted tank. Just pump pressurized Co2, Aquarium dimensions are 18″h×18″w× 24″L. 147ltr/33g. Twin T8 fluorescent tubes, Fluval 306 canister filter.
    I will re-aquascape to improve water flow. I will check back in with you with my results after a week or 2. Plants are mostly Crypts, some Bucephalandra and Anubias, an unknown stem Plant that does well with banana Plants. Thank You!!!

  17. Hi Richard,
    I’m having trouble with hair algae in a three week old 180l tank, stupidly i was leaving the light on for ten, yes ten! hours and obviously got hair algae. After searching the web for ages I came across your article and immediately reduced lighting to eight hour and upped my CO2 injection and ferts and did more water changes. My question is I’m two weeks into my new regime with no obvious difference, how long should the turn around take ?

  18. Hi I’ve just read this thread, trying to find a solution to my hair algae problem. I have a small 60ltr tank which is very heavily planted. I have slow growing Anubis, java fern, tiger lotus and a mixture of very fine grass and a small leafed carpeting plant (not sure the names sorry) which I was under the impression that it needed alot of light. Hair algae is spreading to most plant but mostly on the carpet and grass plants at the bottom.

    Last week I lost 4 cherry shrimp which was not good! So I did a huge water change and everything now seems fine. I did use an anti hair algae dosage (once a week for 2 weeks) which I have now stopped as I was worried this was the root of the problem although it does say it’s safe for shrimp..

    Ive began doing a 20% water change 3 times a week. Before I was dosing ferts twice a week as recommended on the bottle and I only tended to run my co2 occasionally because my plants pear most days and my indicator shows a very bright yellow/orange which suggests there is a very high concentration of co2?

    After reading this I’m going to drastically reduce the light hours as I’ve been running for about 10hrs an day thinking my plants needed it. I’m hoping now with these changes I will see an improvement to the healt of the plants, but at this stage my biggest concern is health of my shrimp.

    If anyone has any advice on any of this then I’d be keen to know. It’s all fairly new to me.



  19. I was pointed to this post as I had hair algae growing quickly and starting to make the tank look a mess. Within 24 hrs of reading this post, and putting all the steps in to place, my hair algae had gone. I reduced the intensity of my light by 25% and reduced from 8hrs to 6 hrs, did a 50% water change after the lights went out and got rid of as much hair algae as I could, gave a double dose of fertiliser straight after the water change and added some Seachem Flourish Excel – there was no hair algae when I woke up in the morning. An hour before lights on I upped the co2 from 2 bubbles per sec to 4 per sec and no hair algae has grown since, it’s now 48hrs since the first big water change and collection or nuisance algae and no new growth. I’ll do another big water change tomorrow evening, after lights out and do the same doses as before.

    Great article and if you are able to do all the steps including co2 injection then the advice is bang on !

    Thank you !

  20. I found your article very informative. Whether it is the preventive or the actual cleaning process, it must be done consistently to prevent algae from overgrowing in your fish tank.

Leave a Reply

Your email address will not be published.


This site uses Akismet to reduce spam. Learn how your comment data is processed.