# [Wet Thumb Forum]-Green Spot Algae



## imported_jerime (Apr 15, 2004)

I know there is some argument regarding PO4/NO3 ratios and PO4's role in GS algae control, but here is my experience in this subject.

It's been more than a year since I had any GS algae (don't remember myself cleaning the glass). I have NO3 = 10-20 AND PO4 = 1-2 usually (ratio range of 8/12 : 1).

Last week I noticed some GS forming on my glass. I my understanding, I figured that something had happened to my PO4 (I neglected dosing it for a while







). when I checked it, it was 0.2 instead of 1.2 that I had before.

Few days of extra PO4 dosage erased the GS completely off my glass - No manuall cleaning.
My specs at the mom are NO3=10+PO4=1.2.

I don't know if the ratio is the issue here ore PO4's role in the plant or both of them but it works. I managed to isolate any other element as dosing, besides PO4, stayed the same.


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## Roger Miller (Jun 19, 2004)

If one were to draw a conclusion based on your experience then the only conclusion I see possible is that PO4 is selectively toxic to green spot algae.

Is that the conclusion you intend to draw?


Roger Miller


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## imported_jerime (Apr 15, 2004)

Hi Roger, knew you'd jump...











> the only conclusion I see possible is that PO4 is selectively toxic to green spot algae.


Absolutely not.

First, it works, so I find arguing with it to be very difficult. The issue here is how can we explain that, as anyone can test it for himself and see if it works.
2nd, I think ratio does have something to do with it, although there are those which oppose it.

The same phenomenon occurs when we have a spike in NO3 level - you get GS algae almost immediately. lowering NO3 in that case would have the same effect so it must be something with to do with this ratio.

Almost every time I see GS in my tank, I understand 1 of these 2 nutrients had gone wild (either NO3 got boosted up or PO4 gone the other way). when I check my water, I see that I'm right. I have to do only 1 action - adding more PO4 or lowering NO3. GS algae vanishes after that.

I think that the ratio between PO4 and NO3 influences plants rate of uptake, thus influencing this type of algae.

If not, what other explanation can you suggest?


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## Roger Miller (Jun 19, 2004)

> If not, what other explanation can you suggest?


I don't know that an explanation can be suggested on the basis of your observations.

The problem is that the green spot algae doesn't simply stop growing. It goes away. I don't know what there is about the nutrient concentration or the nutrient ratio that will make something die and go away.

If there is no mechanism in the concentration or in the ratio that would cause the algae to die, then some other cause needs to be found for the observation.

Roger Miller


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## MOR B. (Oct 9, 2003)

> Originally posted by Roger Miller:
> If one were to draw a conclusion based on your experience then the only conclusion I see possible is that PO4 is selectively toxic to green spot algae.
> 
> Is that the conclusion you intend to draw?
> ...


from my experience gs algae doesnt just dissapear. if u have the right ratio of ferts -maybe its fading and stop growing. the spots that were there probably eaten by oto's or whatever. 
as long as the gs are only on the glass i dont c a problem and i even like it as in this very conditionsthe plants seems to grow faster and healthier and the only thing i need to do is to "wash" the glass with the magnet.

when gs algae is growing on plant leaves - that is a problem one must solve.


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## imported_russell (Sep 14, 2004)

i have had gsa with 3.5 ppm po4, and now i don't have gsa and my po4 is at 1ppm. so IMO that rules out po4 being an algae killer.


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## Pete City (Sep 18, 2004)

Slow growing plants seem to always have a touch of green spot on older leaves.
Culprits for me are, hottonis palustris, lobelia and Lysimachia.
I've stopped measuring PO4 and NO3 some time ago and every few months find a little green spot algae on my glass, nothing that a good scrape can't take care of.
I also dose using the Estimative Index.


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## Maurici (May 31, 2004)

I agree with the assumption that shortage of a nutrient can give an algae increase and solving the situation algae growing can (not ever)stops quite quickly. 
I also agree that PO4 increase involves a GS bloom easily if there is not a deficiency of it on the tank. 
And finally I also think as you that GS disappearing completely only in a few days is uncommon and I have no direct explanation about it; I have these clorophytes as not extremely quickly and good resistant to unpleasing environmental conditions for them.


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## imported_russell (Sep 14, 2004)

> Slow growing plants seem to always have a touch of green spot on older leaves.


my dang anubias


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## imported_jerime (Apr 15, 2004)

> i have had gsa with 3.5 ppm po4, and now i don't have gsa and my po4 is at 1ppm. so IMO that rules out po4 being an algae killer.


I think that the issue here is the ratio. as I said, when you see green spot, it's either PO4 went down or NO3 went up.

In every case I've seen till today (many of them in my forum), treating with PO4/NO3 did the trick. it never came back, unless this rartio was broken.

Pete City, I have Anubia nana. It's clean at the mom. same trick.
If you have GS on your Anubia, check your PO4/NO3 and we'll see...


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