Maintenance and cleaning Fish Tank Guides

Aquarium Algae Infestations

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A guide on defeating aquarium algae


Aquarium Algae can become unsightly rather quickly in an aquarium and is a regular concern for aquarists.  So here I’m going to give you a hand in the (in some case) never-ending battle against algae.  We’ll do this by helping you to identify what kind of algae you have whilst covering some simple remedies and preventative measures that you can take against it occurring to start with.


Where does Algae come from?

The first question most people ask is where do algae come from in the first place?  Algae is just about everywhere, it is in the water you fill your aquarium with, it is in the air you breath, everywhere.  It’s just in such small quantities that you don’t notice it until it starts growing.

It’s also quite hardy and can live and multiply just about anywhere, given that it has some food.  All aquarium algae really need to thrive is light, but it will also use phosphates in your water as nutrients, it will also use your fishes waste, along with any other inorganic matter in the tank.  So it’s not surprising that once you get some algae, it can quickly take over.

algae and moss on rock



Types of Aquarium Algae

There are several types of algae that can affect your freshwater aquarium, I’ll list the common types with a short description, if this is an issue that you are having then hopefully this will help you identify what type it is.


Brown Algae (Diatoms)

Brown algae are very common in aquariums, especially in new setups.  They are hardy and can survive with very little light.  Brown algae initially appear as a brown dusting on surfaces in your aquarium, but it can quickly build up.  If this does appear in your new aquarium, as I say, it’s common so don’t panic.

Simply clear it off hard surfaces as much as possible, hoover your gravel and keep up with water changes.  As your aquarium matures the issue should go away providing you keep up with maintenance.  Most algae eating fish, snails and shrimp thrive on this stuff too, so maybe add one or two that are suited to your aquarium to take care of it.

Aquarium algae



Green Hair algae

Green hair algae can appear in various forms, it can be in clumps or it can be in strands all across your tank.  It looks how the name sounds, green and stringy.  Green hair algae can be a bit of a pest, and again it often appears in new setups.  Usually, it doesn’t do any real harm but it can certainly ruin the look of your aquarium.

The best way to battle these aquarium algae is to again keep up with maintenance.  Regular water changes where you use a syphon to suck it out of the tank will certainly help, or if it really stuck on there, you could use a toothbrush (a priceless piece of maintenance kit) to twizzle it off whatever it is stuck to.  Again as your aquarium matures, this will become easier to deal with.




Black beard/bush algae

This stuff can be a real pain.  It’s tough and stubborn and there are limited fish/invertebrates that will actually eat it.  It appears how it sounds, like little black beards hanging from plants, decor and equipment and once you have it it can pop up everywhere.  It is very difficult to remove, particularly from plants, so if a plant is badly affected by it then its often best to remove the plant.

Most remedies for this require chemicals that will harm your fish if not properly cleaned off afterwards, such as bleach.  So far I have found one species of fish that will eat this stuff – Siamese algae eaters.  Not to be confused with the Chinese algae eater or the flying fox, both of which will be of no help to you against this stuff.




Green Water

Green water is caused by millions of single algae cells floating and living in your aquarium water.  Often the cure for this is regular maintenance, good filtration and not overfeeding your fish.  Leaving the lights off for a few days can also help, as can adding live plants who can out-compete these algae for food and nutrients.

Another option is to add a UV steriliser to your set up.  Some filters come with these built-in, I’ve tried them in the past but always found maintenance and a mature filter work better.  Maybe they have improved now though.




Blue-Green Algae

BGA can be bright green, brown, or even have a red tinge to it. It starts as a thin layer on surfaces in your aquarium but can build to become a thick layer of slime. This stuff can take over and the best solution, if this appears, is to totally blackout your tank until you are confident that it is all gone. That means covering your tank completely, by taping black bags or blackout sheets around it so that no light gets in.

There are other methods but they involve chemicals that will harm your filter bacteria and possibly your fish.  So that may leave you with an uncycled tank and a new list of problems.  Whilst you perform this blackout, ensure you keep up with your maintenance routine and remove as much of it as you can, this will only help to speed things up.  Blue-green algae isn’t actually an algae at all, it is a cyanobacterium, not that that information helps if you have got it in your tank.




Staghorn Algae

Staghorn algae are very similar to green hair algae, but this one, instead of being single strands, branches out a little to look like a stag’s horns.  The treatment for this is also the same.  Regular maintenance and removal.  Good water movement in the aquarium also helps to prevent it from settling.




Prevention is easier than the cure

The aquarium algae listed above are the types that you will most likely have issues with at some point in your fish keeping.  Most other types simply rub off the glass whilst you do your normal maintenance and water changes.

Preventing aquarium algae from occurring is arguably the best solution to any type you might encounter.  There are a few simple steps you can take to give yourself the best fighting chance in any algae battle you may encounter:

  1.  Minimal lighting:  Lighting is food for algae, if you have your lights on too long you are simply feeding it more.  So unless you have a lot of plants that require an extended period of light, then keep them on for just a few hours a day.  Having the lights off will not bother your fish at all, most will prefer it.
  2. Water movement:  Having good water movement can prevent algae from settling on surfaces of your aquarium, it will certainly slow it down at least.
  3. Plants:  Plants compete with algae for nutrients and light, adding live plants to your tank will certainly deter any mass algae colonies from forming.
  4. Don’t over-feed:  Leftover food in the aquarium puts phosphates into the water.  Phosphates are a rich nutrient for algae.  Some fish foods contain higher levels of phosphates, if you are having constant algae issues then consider testing your water and changing foods.
  5. Maintain good water quality:  Keeping up your maintenance and providing clean clear water will certainly help fight back the algae at all stages. You can learn more about this here.
  6. Add an algae eater:  Adding algae-eating critters to your aquarium before you have any algae can prevent any build-ups occurring.  Just make sure that if there aren’t any algae there to eat, you feed them some (algae wafer/spirulina). Learn more about Algae Eaters here.


Remember too that aquarium algae occur naturally, so if it appears in your aquarium, it usually means that you are doing things right.  Unfortunately for the algae though, we don’t tend to enjoy having it in our aquariums, so I hope this helps in any of your current or future battles.

About the author

James @Seriously Fishy

I am a fish keeping enthusiast with over 20 years experience. I currently keep American Cichlids (CA) which are my favourite fish to keep so far. I started Seriously Fishy as I noticed a large volume of people on various web pages looking for help with Aquarium basics. I created the first Seriously Fishy book to solve the issue in 28 pages, that led to the Seriously Fishy UK fish forum and blog.

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