Here’s a scenario for you: You take care of your aquarium by the book but suddenly there’s a strange black fuzzy growth that’s now covering everything.
Scrubbing it removes the stuff for a while but it keeps coming back.
At first, it appears as black mold, often, in a freshwater aquarium environment and it later develops to a beard-like growth. It’s progressively attaching itself to plants, décor, and rockwork.
Is it there to stay?
Are black algae in the fish tank bad for aquatic life there?
After months of fighting it, I really got to know it and finally, I found the cure.
Or cures.
Let’s cut to the chase here.
Quick overview of what Black Beard Algae is
Despite its color, Black algae, also known as Black Beard Algae is a member of the red brush algal family in the Rhodophyta division.
In fact, in some cases, it can actually appear bluish or green-ish in coloration.
It does not only infest aquariums but also pools, ponds and other artificially-managed bodies of water.
It’s very persistent and is often difficult to remove because it has a tendency of returning.
It’s soft to the touch and appears like patches of dark hair, hence the name.
With the right approach, permanent removal of beard algae is possible, however.
Algae grazers such as the rubber lip pleco, The TRUE Siamese algae eater, the American flag fish and the black molly can help immensely.
The issue, however, should be resolved at its core.
Here’s how a heavy black beard algae infestation looks like in an aquarium:
How to remove black beard algae from your aquarium once and for all?
Despite being really good at exploiting nutrients, this invader has weaknesses. I’ve done my research and eventually found a couple of solutions.
They have all been tested in my or other people’s fish tanks. I am now confident to share them with you.
To get rid of the black beard algae in your aquarium for good you should:
1. Dip all of the affected décor in Hydrogen Peroxide
This can be done with a regular over the counter peroxide (3%).
This method is often used for fungi treatment on new seeds right before their germination.
Bear in mind that the more gentle plants (Japanese Moss balls being one) may take damage as well.
However, it’s worth taking the risk considering you’ll get rid of that black beard algae.
If you only have plastic plants you can even use bleach in a 1 to 20 ratio, although peroxide will work too.
Soak all the décor that is visibly affected for 2 to 3 minutes (use a timer!) and then rinse thoroughly.
The nice thing about peroxide is that it leaves virtually no residue and you can instantly put your plants and rock back in the aquarium.
I know that soaking in pure peroxide might seem a little radical, but in my experience, black algae are really hard to banish.
Simply dosing teaspoons of peroxide in your fish tank water won’t cut it.
2. Reduce phosphate (PO4) in the water
Phosphates are a byproduct of almost everything that decays in your aquarium.
This includes leftover food when you accidentally overfeed, plant and algae decay, even fish waste.
However, phosphates will also spike with the use of carbon filter media, hydrogen ion buffer solutions (pH buffers), kH buffer solutions and aquarium salts.
If these sound like way too many possible causes, know that I haven’t even revealed the main one yet.
The tap water itself.
- In some city areas old lead plumbing is still being used.
- The local water authorities, however, found a clever way to fight the lead corrosion in the pipes.
Lead poisoning is quite dangerous so they figured that adding some phosphates to the water (which are basically harmless) will prevent said corrosion.
It’s a smart move to test your tap water for PO4, which can be the hidden reason behind your aquarium algae infestation.
Black algae thrive in phosphate levels of 1 ppm and above so your testing results need to be rather precise. One of the more reliable Phosphate testing kits that I would recommend is , but you can research other brands as well, if you have the time.
Anyhow, if you suspect that your tap water is the issue, then you have two options:
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Find another source of water for routine water changes – Distilled or purified water with reverse osmosis (this is a guide I wrote on which one to use) will surely starve your black algae.
If you revert to this solution know that this water needs to be remineralized before adding it to the aquarium.
Purification clears all minerals – the good AND the bad.
A phosphate-free remineralizer I found, that does wonders is Seachem Equilibrium.
- Introducing phosphate absorbing media to your filter – If you end up getting a PO4 absorbing media, make sure that your filter turns the water in your fish tank at least 5 times per hour.
It’s worth pointing out that phosphate-rich tap water is behind 80% of the black algae problems in fish tanks (no science behind this number, I made it up to illustrate my point).
It was the reason behind my tank’s infestation.
And also the tanks of a couple of friends I helped. And three guys on a fishkeeping forum.
However, if your aquarium water tests read high PO4 and the tap water shows values below 0.25 ppm (which is considered safe) there are a few ways to lower it by eliminating the causes.
To lower phosphate levels in an aquarium you can:
- Add fast-growing floating aquarium plants – most freshwater floater plants have an enormous hunger for nutrients in the water column of your fish tank. They grow super fast and therefore need a lot of food, which includes Phosphates. I’ve got a quick list of 15 floating aquarium plants that you can check out.
- Replace current food – PO4 is used in the making of flake foods, but there are ones containing less phosphate. Elos is a brand that comes to mind as I know for sure that they make efforts in adding as little phosphate as possible.
- Feed your fish sparingly – uneaten food will eventually release phosphate and encourage black algae growth. Dosing meal portions is vital and you should take the number and type of fish you have into account.
- Clean the tank more often – As redundant as it may sound it’s a good idea to go one further on this one. Food and other debris are the usual suspects for phosphate build up in your water.
- Clean the filter – Filters are known to hold enough muck and residue that will eventually spike the levels of PO4.
- Opt for a carbon media with phosphate absorbers – This is for freshwater fishkeepers. Saltwater carbon filter media is often made in a way that prevents phosphate build-up.
- Review your water conditioners – These often have PO4 in them. Everything that treats water from buffers to pH alteration products contains a good amount. Do yourself a favor and research them well, before buying.
3. Feed your plants by boosting Carbon Dioxide.
Whenever the CO2 levels in your aquarium become low your aquatic plants find it hard to extract the needed amount from the surrounding Hydrogen carbonate.
Black algae, however, is really good at that and it will outcompete your plants and thrive.
When this happens your pH will elevate, which is a really good sign that a poor CO2 level is your problem.
In an aquarium low on carbon dioxide, the algae will be stiffer to the touch and even the Siamese Algae Eaters won’t bother munching on it.
By raising the CO2 levels in your aquarium you give your aquatic plants a kickstart to the competition for nutrients and the eventual starvation of the algae.
Soon after the effect takes place the BBA will become weak and therefore an attractive snack for your algae eaters.
Two stones with one bird, so to speak.
Aside from a gas cylinder and a CO2 regulator with functioning solenoid, another way of introducing more Carbon Dioxide to a fish tank, in terms of efficiency, is with Seachem Flourish Excel.
Aim for 20 to 25 ppm, granted that your Oxygen levels are in the healthy range.
Don’t forget that carbon may spike your phosphate.
4. Introduce black algae eating fish to your fish tank.
The true Siamese Algae Eaters (SAE for short) are known to feed on black algae.
There’s a catch, though.
Hard, unappetizing algae is a result of low carbon dioxide in planted tanks. They use the limescale precipitate in a process that hardens their wall cells.
This method should be combined with either the peroxide soak or the CO2 injection method.
Both methods will render the algae weak and soft enough for your SAEs to feast on it.
Many people I know report that after weakening the algae a sudden interest from their algae-eating tank pets occurs.
That being said, true Siamese Algae Eaters (visit the link for more info on this fish) are not your only friends when it comes to an appetite for algae.
You’ll be surprised at how diverse the reports are on what else eats black beard algae in aquarium habitats.
Here’s a full list of reported fish that will eat black algae:
- American Flagfish
- Black Molly
- True Siamese Algae Eater (young ones, as they pick the habit of feeding on the stuff)
- Chinese Algae Eater
- Twig catfish
- Bristlenose pleco
- Rubber lipped pleco
- Pigmy suckermouth
- Rosy Barb
- Cherry Barb
- Common Goldfish
The Amano shrimps are also avid black algae eaters.
Side note: Let me know in the comments if you’ve seen other fish feasting on BBA, so I can expand this list further.