# Cyanobacteria within substrate - should I be concerned?



## Chris_Homan (30 Sep 2021)

I had a small Cyanobacteria outbreak which I thought I had treated successfully. However, I can see through the front pane that there are still Cyanobacteria lower in the substrate. Is this something to worry about?


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## castle (30 Sep 2021)

Fairly normal for me in my tanks. A healthy tank above should keep it there 👍


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## tam (1 Oct 2021)

Tape a piece of card along the substrate, that will block the light and knock out those last bits - leave it for a week or so. You can also, carefully not to scratch the glass, use a credit card to run along the front edge and syphon it out. It will only be along the glass as it needs light.


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## HarrietHippo (1 Oct 2021)

Can also spot injection Flourish Excel if you like as well to eradicate


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## castle (1 Oct 2021)

HarrietHippo said:


> Can also spot injection Flourish Excel if you like as well to eradicate



This didn't work for me



tam said:


> Tape a piece of card along the substrate, that will block the light and knock out those last bits - leave it for a week or so. You can also, carefully not to scratch the glass, use a credit card to run along the front edge and syphon it out. It will only be along the glass as it needs light.


 
While this will work, it wont remove 100% and risk of glass scratching is high (depending on substrate). BGA can survive longer than a week without light tho


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## bazz (1 Oct 2021)

tam said:


> Tape a piece of card along the substrate, that will block the light and knock out those last bits - leave it for a week or so.


This didn't work for me either, seems the light is refracted down within the glass itself and was still illuminating the outer edge of the substrate.
Fortunately for me it never breaks out of the substrate.


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