# Green Spot Algae, Phosphate deficiency?



## solarz (Aug 31, 2010)

I've been having green spot algae on glass for a few months now, and recently, I read that GSA is caused by low phosphate or co2, and that adding phosphate should clear it.

The thing is, I just can't fathom my tank to be low on phosphate. There's always plenty of Nitrates, and as far as I understand, Phosphate should be just as plentiful in fish foods. (I don't do any fertilizing apart from some Potassium.)

I'm using a DIY CO2. Should I try to add phosphate to the tank?


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## tranceaddict (Apr 3, 2011)

Plants absorb 400x more nutrients though their roots then anything else. A good substrate solves all. lol but yea looks like you need to add some nutrients, by dosing.


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## Roberacer1 (Aug 21, 2010)

*green spot algae*

you mentioned green spot algae but didn't indicate where. On the plants or the glass, rocks ETC. It is my understanding that that kind of algae (on non living surfaces) is a good thing in small amounts as it indicates good water conditions. When it grows on the leaves apparently that is a different story. As far as fertilizing you may not need to do much. You are correct that as the food and fish waist break down they do in fact feed the plants. That said there are certain elements that don't come from the food or waist and therefore need to be added. You also mentioned that you are using CO2. A home unit you say. Non the less it is possible to add too much CO2 even with that depending on other factors like your specific PH and DKH levels. Also lighting will affect how rapid the plants uptake nutrients. 
If you are growing lots of algae I would suggest that you might have too much phosphate as that is normally what encourages algae to grow. Particularly green algae. You don't need to guess though. I have a phosphate test kit. They aren't that much money at any LFS and that will answer your question right away. 
If you have algae growing on the leaves of your plants it could be that the plants are somewhat nutrient starved (fertilizer) as well as the phosphate levels are elevated encouraging algal growth. I would test it. That should tell you something.


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## solarz (Aug 31, 2010)

I don't have problem with any algae except the Green Spot Algae. There are some GSA growths on hygro leaves, but they seem to be mainly on old leaves, and the hygros are still growing like weed.

It's mainly the GSA on glass that annoys me. The back and side panels are covered with this, and the front panel would be too if I don't scrub it off from time to time.

Another issue is that this could turn out not to be GSA at all. I used to have a lot of green hair algae before I started using CO2. At the same time though, I also introduced two SAE and Amano shrimps, so sometimes I wonder if what I'm seeing could be the "roots" of hair algae?

I've read from posts by Tom Barr on other forums that Phosphate doesn't cause algae, and its deficiency is in fact a cause of GSA, which is why I'm suspecting a PO4 deficiency.


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## destructo (Aug 12, 2009)

I found that my zebra nerite snail got rid of the GSA in my tank with the exception of the GSA on my crypt and java fern leaves.


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## Roberacer1 (Aug 21, 2010)

I certainly won't claim to be an expert so please excuse me if my phosphate understandings are wrong. Here's what I have seen. When I set up my discus tank I used a product called "discus buffer" by Seachem to get the ph to the right level. I didn't know this but discus buffer is a phosphate product. My tank began to grow algae like crazy. I will say that in the beginning it was mostly red (BBA) though. It wasn't long and it grew both red and green (spot algae). I had to buy a phosphate test kit and phosphate absorber pellets (phosgard-seachem) to correct the problem which took many months. Maybe 6 overall. One could see a direct co-relation between changing the phosgard and the algal growth levels (both green (spot mostly) and red. As the phosgard aged, algae would grow. A day after or so after changing the phosgard one would notice a significant decrease (simanese algae eaters and a nice mustard spotted pleco). Not to mention the plants didn't like me sucking all of the phosphate out much either. The test levels sat very close to 0 ppm. I would allow it to get to .25 ppm before I would change the phosgard. It cost me a fortune in the stuff too. I should also tell you that there are other parts to this story but they aren't really relivent. Suffice it to say in my practise something seems weird with the Tom Barr theory.


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## Zebrapl3co (Mar 29, 2006)

Robracers, your understanding of phosphate is more or less correct. You just need to keep a good balance of things.
Tom Barr's method is an estimate, so it's never perfect. You'll need to tweaking it to fit your tank. And thus, that's why it's working for some and not for others. Also, water change is the key, if your ferts are not dead on accurate, even 1 day late on your water change can lead to out of control algae growth. Then there is the fact that the nutrient requirement for fertilization changes as your tank matures. That same formulae which worked like a charm at start up, will not work 2, 3 or 4 months down the road.

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## Roberacer1 (Aug 21, 2010)

So in short what you are saying is phosphates either low or high can result in the same problem? Is it likely to be an issue with phosphate at all then? No-one seems to actually know with BBA. Officially, there seems to be no cure for that.


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