# Help with GSA



## nhung (Aug 3, 2009)

I have green spotted algae on my tank glass and some starting to grow on my anubias. I read GSA is caused by PO4 deficiency. I have added 1ppm of PO4 about 3 days ago. They are still there. Do I need to wait longer?

Other parameter.
nitrate 10ppm
ph 7.2
GH 150ppm

I do not have CO2. I do dose excel.


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## Seattle_Aquarist (Mar 7, 2008)

Hi nhung,

I did not find Excel to be effective against green spot algae (GSA). I suggest reading this interesting post by Christian Rubilar, "Method of controlled imbalances and gda...". The first part deals with dealing with green dust algae (GDA) by increasing KNO3 dosing until GDA disappears and GSA appears. The second part deals with increasing the dosage of PO4 until the GSA stops appearing. From what I have read, the existing GSA does not disappear it just doesn't continue to spread to new growth. I am trying this procedure myself.


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## nhung (Aug 3, 2009)

Thanks Seattle


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## nhung (Aug 3, 2009)

What type of algae is this? How do I treat it?


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## Seattle_Aquarist (Mar 7, 2008)

Hi nhung,

It is a little hard to tell from your picture. If it is blackish, and forms little tufts of strings, it is probably Black Brush Algae (BBA). I have used Excel (and glutaraldehyde) dosed at 2X normal dosage to combat BBA. If there isn't a lot of it, I have also used a syringe filled with the 2X amount and "shot" the tufts of BBA with good results. BBA said to be caused by low CO2 levels, which should be checked and corrected to prevent reoccurrence.


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## nhung (Aug 3, 2009)

Thanks SA.

You're the only one to reply to any of my post . I thought it was BBA too. I have tried excel. It does not work. I can't seem to rub it off either. I will try h2o2.

Again, thanks for your help.


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## p-daddy (Oct 4, 2009)

Seattle_Aquarist said:


> Hi nhung,
> 
> It is a little hard to tell from your picture. If it is blackish, and forms little tufts of strings, it is probably Black Brush Algae (BBA). I have used Excel (and glutaraldehyde) dosed at 2X normal dosage to combat BBA. If there isn't a lot of it, I have also used a syringe filled with the 2X amount and "shot" the tufts of BBA with good results. BBA said to be caused by low CO2 levels, which should be checked and corrected to prevent reoccurrence.


I am going to try this syringe method!


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## nhung (Aug 3, 2009)

I finally took the plant out and dip it in 3% H2O2. It killed of the algae, but some of the leaves also turn brown.


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## Seattle_Aquarist (Mar 7, 2008)

Hi nhung,

I typically do not use Hydrogen Peroxide (H2O2) or Bleach treatments except as a last resort. Some plants seem to be very sensitive to these two treatments. Then only plant types that Excel seems to have an adverse effect on is Vals and maybe Sags.


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## nhung (Aug 3, 2009)

I guess the anubias did not like the H2O2 treatment too much. About half the leaves have turned brown. I guess I will only use Excel next time. Thanks for the advise Seattle Aquarist.


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