# Very good info on GDA/BGA relationship



## bsmith (Dec 13, 2006)

I started a thread over at TPT because i was absolutely fed up with the amount of GDA I was dealing with in one of my tank. Over the course of quite a few different trials ranging from adding more of this and less of that to medicating the tank with Erythromycin what I found is this.

I had excessive amounts of GDA after sending some samples of the algae in the tank to someone with a microscope and baisic knowledge of cell structure it turned out that I indeed had Blue Green Algae/BGA/Cyanobacteria in the tank. You might be wondering what the heck bacteria has to do with algae.

Here is what it boils down to. The massive amounts of GDA I had was caused because the BGA was sucking up all the Nitrogen I was dosing in the tank. This caused my plants to in turn grow poorly and not be able to out compete the GDA so i took over.

I started dosing my tank with API E.M. Erythromycin and after 2-3 days I could already notice a vast improvement in my plants health. After the medication treatment was done (6 days) I thoroughly cleaned the tank and filter. Now, roughly a week after completing the treatment the GDA is only what one could expect in a high light high tech setup (cleaning the glass once a week with a mag float) and the plants are growing beautifully.

Here are the two threads that I started that contain much more info then I just surmised. The first is the original one I started and the second is one I started for another tank that is suffering from a similar problem with Cyanobacteria. Symptoms are similar but the appearance of the BGA is completely different.

Original thread in which I was just looking to get to the bottom of GDA

A secondary thread on another tank where Cyanobacteria is the culprit again

If you have any questions or experiences with this issue please post them up. Hopefully some people will get some good help from this!


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## Silvering (Jun 10, 2011)

That was absolutely fascinating reading, bsmith, thank you for sharing! 

Unfortunately I don't really have any additional info to share; I got "green paint algae" (almost certainly BGA mixed in) in my (non-planted, bare bottom, sponge filtered) 10g quarantine on several occasions but generally solved that problem by wiping down the glass and doing a 100% water change. Direct sunlight did make a big difference in rates of growth, when I moved that tank to a different wall it took much, much longer for the GPA to come back, and I didn't get curtains of BGA. Now I have some Java moss in that tank, I guess I'll see what happens!


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## bsmith (Dec 13, 2006)

Im glad you got some use of the info. It's just that there are many different battles that we have to fight in this hobby and shedding light on this one will hopefully make some peoples battle easier.


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## Bert H (Mar 2, 2004)

Interesting thread bsmith. that reminded me that several years ago, I played with maracyn and apparent gda. http://www.aquaticplantcentral.com/forumapc/algae/50181-maracyn-gda-experiment.html Looking back on it, I'm sure it was a combo bga/gda issue. In any case, I'm glad things worked out for you. In your opinion has adding extra Mg made any difference?


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## OTPT (Sep 27, 2010)

bsmith said:


> --re is what it boils down to. The massive amounts of GDA I had was caused because the BGA was sucking up all the Nitrogen I was dosing in the tank. This caused my plants to in turn grow poorly and not be able to out compete the GDA so i took over.--


Did you test for nitrate level before coming up with the assumption?
It's hard for me to believe algae could deplete N that much.
Cyanobacteria is known for its toxicity to other plants and animals.


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## bsmith (Dec 13, 2006)

Bert H said:


> Interesting thread bsmith. that reminded me that several years ago, I played with maracyn and apparent gda. http://www.aquaticplantcentral.com/forumapc/algae/50181-maracyn-gda-experiment.html Looking back on it, I'm sure it was a combo bga/gda issue. In any case, I'm glad things worked out for you. In your opinion has adding extra Mg made any difference?


Adding extra Mg did nothing to help the problem. It was only when I was at the end of my rope and was shown the relationship that Cyanobacteria has with N in our tanks that I started dosing the Erythro.


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## bsmith (Dec 13, 2006)

OTPT said:


> Did you test for nitrate level before coming up with the assumption?
> It's hard for me to believe algae could deplete N that much.
> Cyanobacteria is known for its toxicity to other plants and animals.


Not before I started dosing the Erythro. About a day afterward I tested and the levels were almost non existent. Keep in mind I was dosing .5tsp every other day with Kno3 for Nitrates and that I also have ADA AS substrate. After I completed the dosing and cleaned the entire tank including the filter I checked again and then the N numbers were more inline with what they were in the past which was in the 10-20ppm range.

Cyanobacteria is a N fixing organism. With it and GDA rampant in the tank there was no way to keep N levels sufficient. Then my plants stopped growing properly and this only exacerbated the GDA issue.

The only thing I still am not 100% clear on is if the low N levels are what cause the BGA/Cyano to start thriving or if the BGA/Cyano just cause the low N. I believe the latter since it just makes more sense but I have no scientific proof of that.


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## OTPT (Sep 27, 2010)

bsmith said:


> >>he only thing I still am not 100% clear on is if the low N levels are what cause the BGA/Cyano to start thriving or if the BGA/Cyano just cause the low N. I believe the latter since it just makes more sense but I have no scientific proof of that.


Ya that's the point (of this subtopic-don't want to ruin the main 
focus on BGA and GDA relationship), whether low N is the cause or effect.
The consensus is it's the cause. Tom Barr mentioned 
anaerobic condition in filter/sediment can make nitrate 
evaporate out of the tank via denitrification.

I said it's hard to believe because seeing the mass of BGA and GDA.
They shouldn't have that much capacity to deplete nutrients to the 
point plants suffer. Not much scientific based also.


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## Silvering (Jun 10, 2011)

op2:

To further derail this topic, why is the consensus that low N causes BGA? (And how "low" is "low"? None? Fractions of a ppm?) That doesn't seem to match up with when I've seen it in non-planted tanks at all, but I've never tested consistently enough to have any hard evidence about N levels, and it's possible that N could have been drained by other algae species before BGA got a foothold. 

I can totally believe that an advanced case of BGA symbiotically paired with GDA could drain a consistently fertilized tank of nitrates before plants could uptake them. Especially if anaerobic conditions could also accomplish that feat. In both cases, bacteria are responsible, they're just sequestering the N in different ways. 

Now here's a question - how would someone diagnose the problem as BGA/GDA rather than just GDA that can be fixed by fiddling with nutrient levels? Without a microscope!


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## bsmith (Dec 13, 2006)

I have no agenda and these conclusions have just been bSed on my observations and the observations of others. It seems to be oretty common across the board that in tanks where cyano are present that the N levels are super low (<5) or completely depleted at 0. 

The battle between algae in our tanks is always a case where the plants cannot outcompete the algae for nutrients. When the plants are happy algae has no foothold to gain ground. In my tank as soon as the cyano was killed the plants started growing properly and the algae/cyano had not yet returned. How long this will last is still TBD.


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## bsmith (Dec 13, 2006)

Well seeing is believing and now this is a couple weeks after the chemical treatment. I think its very clear and safe to say that with out the Erythro treatment my tank would never be looking as good as it does now.


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## Bert H (Mar 2, 2004)

Quite the difference! :thumbsup:


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## bsmith (Dec 13, 2006)

Bert H said:


> Quite the difference! :thumbsup:


Yes sir! I haven't scraped/touched the glass in over a week and there is barely even the slightest bit of GDA detectable. Its a thing of beauty!!!


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## Kubalik (May 24, 2008)

Thx Bsmith and others that helped , for posting all this , I think i have exactly same situation and going to start Erythro-treatment today .


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