# interesting read, plants use oxygen too.



## fishyjoe24 (May 18, 2010)

I was reading this article and ran across something That I have never herd before. apparently when plants are in low light level conditions they actually use up oxygen. This seems like it might be of interest so some people who have extremely planted tanks



Some reasons for low dissolved oxygen levels are

* a short lighting period in planted tanks, plants produce oxygen during the lighting period and use up oxygen at night
* an overstocked tank, which translates to larger amounts of waste created that in return requires more bacteria to oxygenate the waste
* no or too little water agitation
* waste rotting in the filter or in the gravel

Another term in connection with dissolved oxygen is the Redox potential.

In simple words Redox refers to the relation of oxygen and waste particles. The more waste, the less Redox potential due to lesser oxygen. Redox can be measured in mV and the range should be between 150 to 250 mV.

Redox is also related to the biological oxygen demand (BOD). BOD is the measurement of how much oxygen is needed to break down the waste created. The higher the BOD value, the worse the quality of the water.

An acceptable BOD value is at about 1-2 mg/l (ppm).

Nitrates contribute to high BOD levels, since this generally indicates a high break down rate of waste.

In Biology 1 (highschool) it is commonly taught that plants are in the photosynthetic cycle during daylight hours which produce the sugars needed to 'power' the plant as it goes into the Kreb's cycle during night hours. So basically, at night the plant is using a similar respiration cycle that we use, which uses oxygen and releases carbon dioxide. 

This is not new knowledge by any means. All plants do this. 

As for the term 'Redox pontential' - I have never seen it used for the relationship between oxygen and waste products. Its raw definition is the measure of the ease at which electrons are aquired by any chemical species (molecule), thereby being 'reduced'. This is one of three acid-base relationship theories and governs the measure/calculation of pH.


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## Crispino Ramos (Mar 21, 2008)

Plants are aerobic organisms also. 

http://wiki.answers.com/Q/Do_plants_use_oxygen


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## digital_gods (Apr 23, 2010)

Got a URL to that article? In my heavily planted tank, I have to run aeration at night time. I don't turn my CO2 off, but instead I kick on air pump instead, 30 min before lights out and 30min after lights on.


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## WRabbit (Dec 13, 2010)

Google is your friend.....

It appears this was (completely) gleaned/copied from several posts in a thread on USAFishBox. I couldn't find the article.

Here's a link to the original posts.

*Plants use up Oxygen as well as produce it*

Jim


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## NeonFlux (May 15, 2008)

Plants do take up a little bit of oxygen during the night. That is why some folks use a aerator for oxygen during the night, just in case of a emergency. But it's generally not necessary.


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## HeyPK (Jan 23, 2004)

Plants use oxygen day and night. It is generally assumed that the oxygen consumption is the same whether or not the plant is also photosynthesizing, which it can only do if there is light. _Egeria densa_, for example, in total darkness, has an oxygen consumption of around 4 micromoles of oxygen per gram per hour. This is very low. In comparison, fish consume oxygen at roughly ten times that rate. A plant is like a business. Photosynthesis is income and respiration is expenses. If, over a 24 hour period, photosynthesis exceeds respiration, then the net photosynthesis (photosynthesis minus respiration) is the same as a net profit, and the plant puts the net profits into growth as a good business should.


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## fishyjoe24 (May 18, 2010)

WRabbit said:


> Google is your friend.....
> 
> It appears this was (completely) gleaned/copied from several posts in a thread on USAFishBox. I couldn't find the article.
> 
> ...


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