# Cyanobacteria on surface layer



## Pablos (Mar 12, 2021)

I have very well established tank. It was running without a problem for a year.

https://share.icloud.com/photos/0nTyN8CgzGbooMojxau5NpxIw
https://share.icloud.com/photos/0ZwVRSRyFj2WeYuz5Ns_yh4yw

As you can see it's heavy planted. Livestock : betta, some RCS shrimps which are breeding like crazy and two snails.

Food and soil are providing all necessary nutrients for plants - I don't use fertilizer at all. There is only small passive co2 diffuser. With high level of plants in tank and emersed air monstera roots, small palm there is literally no NO3 and I don't need to change water for weeks to keep my betta happy. I occasionally add evaporated water only.

Everything worked great, but recently I noticed Cyanobacteria on roots of my floating plants. Water Spangles and Duckweed are covering majority of surface, but some are glued with green algae.

Smelly green goo must be Cyanobacteria, however I might double check it and see it under a microscope.

The question is: why out of blue it appears there if nothing changed in the tank?


----------



## mistergreen (Mar 3, 2007)

Cyanobacteria is a nitrogen fixer. You usually see them in new tanks with no nitrogen.

I think it's pretty easy to get rid for you. Remove the floating plants and wash off the BGA, then place the plants back.


----------



## GadgetGirl (Sep 25, 2013)

mistergreen said:


> Cyanobacteria is a nitrogen fixer. You usually see them in new tanks with no nitrogen.
> 
> I think it's pretty easy to get rid for you. Remove the floating plants and wash off the BGA, then place the plants back.


I find this very interesting! I have a Walstad tank that has several VERY robust pothos and syngoniums growing out of it. It is filterless with only a powerhead for movement. I NEVER have nitrates...always zero (and yes, I shake the hell out of bottle #2). And I too am plagued with Cyanobacteria! To the point where I have to treat with erythromycin, which I hate to do. Should I add supplemental nitrogen even though there is soil?

Sent from my Pixel 4 XL using Tapatalk


----------



## mistergreen (Mar 3, 2007)

Whatever nitrogen you add in, your pothos will eat up. Maybe trim the pothos down and feed your fish more.


----------



## Pablos (Mar 12, 2021)

betta is alread quite fat, so I don’t think I can feed it more. 

I guess I know what was a sudden reason on Cyanobacteria build up. I mentioned that I have passive co2 and fuse there was faulty so at the end tank got less co2than usual.
I read that Cyanobacteria might grow when co2 is not stable... apparently it was a culprit in my case


----------



## jake37 (Mar 18, 2021)

Over time the soil can compact producing a type of anerobic bacteria that will consume nitrate and produce gas that will feed a specific type of cyanobacteria. At least that is what happened in my tank. I added a little current to 'disturb' the substrate and it went away.... It took a lot of searching for me to figure out what was happening. The trick is that there are different type of anaerobic bacteria and they produce different type of by-product which has different impact on the tank.... One hint i had of what was happening is the nitrate level stayed around 1ppm despite an extremely dense fish population for several months. I guess that was the positive


----------

