The Bacteria Often Mistaken For Mould!

Updated: Sep 26, 2021

Gloeocapsa Magma

The black staining on this roof top is Gloeocapsa magma...

Not mould!

Gloeocapsa magma on Colourbond roof

Photo - Customer's home (Condon)

At the majority of quote appointments that we arrive at, the homeowners explain to us that it is only since the 2019 flood in Townsville that the dark growth on their roof or other horizontal surfaces has appeared or grown at an exponential rate.

An ancient photosynthesizing cyanobacterium that converts water into oxygen gas, Gloeocapsa magma (Gleo) is the chloroplast ancestor for all of Earth's plant life.

Video - Customer's home (Alice River)


Gleo thrives in high humidity and low sunlight.

For the Condon home above, it grew only on one side of the roof.

Strange...I first thought...Until my research lead me to understand how perfectly natural it is for this bacteria.


First things first!

How does it grow?

Moisture and calcium carbonate (or limestone), often found in roof shingles, nourish this single-cell organism, which supports colony growth and the gradual accumulation across an entire roof surface over time. Gravity then influences its smear-like stain.

How does it spread?

Small groups of cells (spores) detach from colonies and relocate through wind and animals to continue their life cycle, doing this most successfully where there is low light.

Ah, ha!

Ah, ha!

The affected side of the roof in Condon must receive the least amount of light...

Reduced light allows this bacteria to remain green, resembling algae, but it is not algae!

Gloeocapsa magma is bacteria!

Usually green in the shade and black when protecting itself from UV rays.
Gloeocapsa magma at the base of drainpipe

Photo - Customer's home (Kirwan)

Wait! What?

Wait? What?

Why isn't the roof in Condon totally covered in green then?

To protect itself from high UV exposure, Gleo will develop a dark outer coating, such as seen in the roof at Condon.

This sticky secretion further increases this bacteria's durability, as it effectively affixes itself to a surface, remaining even after its death.

Once the bacteria have become noticeable, the stains and damage the bacteria cause will continue to worsen year to year!


There's more...

Symbiotic, or mutually beneficial, relationships between Gleo and fungi (i.e. mould) often create completely different organisms named lichen. See below, how the edge of the concrete has been deteriorated by these organisms.

Video - Customer's home (Alice River)

Damage to Property

The literature reports agreement between the majority of field experts that Gleo is substantially damaging. As this bacteria holds moisture within roof shingles, left untreated, the materials age prematurely, corrode and lose particles, resulting in a roof's inability to reflect UV rays and shortening its life.


  • Increased air conditioning usage = Higher electricity bills

  • Chronic roof repair / reconstruction

  • Earlier roof replacement

  • Inferior property resale values

  • Insurance companies cancelling policies

Human impact...


ALS (Amyotophic lateral sclerosis) is the subject of latest research connected with people experiencing exposure to significant levels of cyanobacteria toxins such as BMAA (B-Methylamino-l-alanine).

BMAA is a neurotoxin, affecting the brain and its ability to control muscles in all parts of the body.

It can lead to Alzheimer's Disease and death, as the brain and body atrophy (waste away) due to the neurotoxin's degenerative effect on nerve cells.

It has been reported that ALS has had a 2.3 times increased chance of development for locals living within 800 m of lakes infested with cyanobacteria.

What Now?
Ross River, Townsville, QLD

Image - Ross River, Townsville, QLD

Spot clean

Options for eradication...

The most common and widely accepted solution is an application of Sodium Hypochlorite and Copper Sulfate. This works well for spot treatments, as there is little risk of toxification to humans, animals, or the environment. However, these days not every family has the time for this :-)

What about larger, more difficult areas?

Gloeocapsa magma

Image- Customer's home (Kelso)

Like your roof (above) or outdoor living areas (below)?

Gloeocapsa magma

Image - Customer's home (North Shore)

Preferred technique

A non-pressure application of a properly proportioned detergent mix...

Low pressure Softwash application
Softwash In Action

Image - Customer's home (Belgian Gardens)

As this will avoid costly damage to...Property.

Softwash - After

Image - Customer's home (Kelso)

Softwash - After

Image - Customer's home (North Shore)

Every home and it's situation is unique...

When treated with our Softwash solution, the bacteria turns from black to a port wine purple colour, as the outer coating is removed to reveal the bacteria beneath (see below).

Exposed bacteria Gloeocapsa magma
Port Wine Smear

Image - Customer's home (Ayr)

Our Condon roof featured in this blog was living with a milder cases of Gloeocapsa magma. Hence, Softwash North Queensland was able to effectively remove it on the day of the clean. Two applications of our Softwash cleaning solution was enough to treat (i.e. kill) the bacteria, before the solution was rinsed off, taking the dead bacteria with it to decompose.

Softwash - After

Image - Customer's home (Condon)

For the roof in Kelso, the infestation was more severe. Therefore, treatment in this case involved four applications.

The most destructive case we have come across involved a 10 year colonisation. The following images speak for themselves.

Gloeocapsa magma growth
10 Years of Colonisation

Gloeocapsa magma has eaten into the paint of this Colourbond roof causing the paint to begin to lift and peel.
Bacterial Damage

Images - Customer's home (Kelso)

These are the occasions when the Softwash solution is not rinsed off (see below), instead being left on to work through the sticky structure of the Gleo without further disturbing any peeling paint.

Heavy Gloeocapsa magma infestation near Ingham
Softwash - Before

Dead bacteria is flaking away and will soon be gone
Softwash Treatment - 3 days after

Images - Customer's home (Toobanna)

Our customers sent us the photo above a few days after the treatment. Colour had returned to the Colourbond as the cyanobacteria were dead, no longer active, and no longer deteriorating this roof surface. On a recent work trip to Mission Beach, we drove passed this home and the roof looked clear. Happy days :-)

Pleased with the results


In preparation for sale, the following Idalia home received a full service. Softwash North Queensland Softwashed the house exterior, including the windows, rear pool and entertainment areas, surrounding aggregate, driveway, and roof. The process of cleaning the Gleo using Softwash is demonstrated in the next three photos with impressive results.

Softwash Colourbond Roof - Stage 1
Softwash Colourbond Roof - Stage 2

Following a full service exterior clean by Softwash North Queensland
Ready for Sale

Images - Customer's home (Idalia)

What about tile and asbestos?

The Softwash process is perfect for tile roofs, as well as asbestos, as the surfactant mixture blankets the surface to do its work and is then rinsed without forcing water into spaces where it's not wanted. This leaves materials in tact and removes only the organic matter that was threatening to destroy them. See before and after photos below.

Suffocating underneath a thick layer of Gloeocapsa magma
Tile Roof - Before Softwash

Tile Roof - After Softwash

Images - Customer's home (Annandale)

Blanketed by a Gloeocapsa magma infestation
Super 6 Asbestos - Before Softwash

Super 6 Asbestos Roof - After Softwash

Images - Customer's home (Mysterton)

Information Sources














  • https://Copper Sulfate (

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