# Does Oxygen kill algae?



## mattmathis77 (Dec 12, 2008)

Are high oxygen levels lethal or unhealthy for algae? Or can it at least slow or limit algae growth?

Thanks!!!


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## StripesAndFins (Dec 31, 2008)

it could since it performs photosynthesis but it would need to be in a plant only tank. if there are fish in there, then there should be no problem. hope this helps.

Also if you lose the algae, please dont blame me


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## TheOldSalt (Jan 28, 2005)

Adding hydrogen peroxide to a tank to raise it's oxygen level is an old trick for getting rid of algae.


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## SueM (Jan 23, 2004)

TOS is right, but no more then 3 drops per gallon.


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## TheOldSalt (Jan 28, 2005)

Ooops.
Right! I guess I should gave included that little detail.


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## jones57742 (Sep 8, 2007)

StripesAndFins said:


> it could since it performs photosynthesis ...


SAF: photosynthesis employs CO2 and not O2!




TheOldSalt said:


> Adding hydrogen peroxide to a tank to raise it's oxygen level is an old trick for getting rid of algae.


TOS:

I had never heard of this one until John described it in one of Fc's threads.

I just flat do not understand the effective reactions for algae reduction. Can you help? (ie. you got all the biology and not Ron.)


This one I also do not understand:

At any given ambient tank water temperature, ambient room temperature and atmospheric pressure (obviously there are other considerations but these are significant) the O2 as well as the CO2 saturation concentration in the tank water is fixed.

The high tech plant folks just keep injecting CO2 in order to overcome this saturation concentration issue.

How do you maintain the O2 concentration above saturation, ie. do you add three drops of HP every hour, every two hours, every day, every week, etc?

TR


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## StripesAndFins (Dec 31, 2008)

Jones: Photosynthesis makes oxygen and needs carbon dioxyde. Trust me, i had a huge test on cellular respiration and photosynthesis. Respiration makes CO2 and needs O2.


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## Fishfirst (Jan 24, 2005)

Both of you are saying the same thing then


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## TheOldSalt (Jan 28, 2005)

Well, no, S&F wasn't saying anything relevant. I must confess that my own response was a bit of gibberish as well. I'll explain:

Adding peroxide does raise the oxygen, but that's not what gets rid of the algae. The process by which it raises that oxygen is what does the trick. You see...

Hydrogen peroxide can pass through cell membranes. ( It also breaks down in the presence of light, which is why it comes in those dark brown bottles. ) The reaction is 2H2O2 -->2H2O + O2, but there are some short-lived intermediate stages. The most important here is that at one point you have OH- and HO+ ions (the dreaded 'free radicals'). HO+ in particular is extremely reactive. It will swipe an electron from any available substrate; ( like algae cell walls ) this in turn converts the substrate molecule into a radical itself, which swipes an electron from the next molecule, and so on. This is extremely destructive within a cell, denaturing proteins and demolishing nucleic acids, resulting in massive trauma to cells.

So why does it wipe out algae but not plants or fish? Plants and fish have protective coverings and multiple layers of cells; the H2O2 cannot penetrate far before it is spent and only harmless H2O and O2 are left. Most algae, as well as microbes, are less well-protected and are easily wrecked by the H2O2.

As for frequency of dosing, most of the leftover oxygen is used up within several hours, so you can dose every day if you wish until the algae melts.

Oh, I almost forgot; having an elevated O2 level will of course also lead to increased nitrification, which means there will be less ammonia in the tank and more nitrate. Vasular plants largely prefer nitrate, but algae have an easier time of "eating" ammonia, so another insult to their injury is the removal of their food. Algae also tend to grow best where plants can't, and the addition of extra O2 tends to generally improve tank conditions enough to tip the balance back to the side of the plants.


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## SueM (Jan 23, 2004)

I have a large piece of driftwood covered in African water fern (bolbitis heudelotii) and *Lace java fern* 'Windelov'. That at least once a year gets covered in black/brown hair algae, mostly on the edges of the leaves. I pull it from the tank & soak it in Hydrogen peroxide for 3 minutes, let it stand for an additional 3 minutes, then rinse & return to the tank. Within a week the hair algae dies off, leaving the pretty green leaves. 
I did not know the science behind it, I only know it works. So thanks for the detailed description TOS.


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## jones57742 (Sep 8, 2007)

TOS:

I very much appreciate the detailed explanation and time which you spent preparing the post! (Believe me: I was really lost here on the O2 oversaturation wrt algae decline!)

I now know why, in understanding nature type terms, my primary physician has me put a cap-full of HP in my ears when I sense that an external ear ache is imminent and subsequently rinse out the "sludge".

TR


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