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I just want to ask how to convert ppm to mV regrading ozone level in aquarium.


Thank u

 Oct 19, 2016

ppm (parts per million) and mV (millivolts) are not compatible!!!.

 Oct 19, 2016

Guest answerer #1 obviously knows nothing about chemistry. His answer is brain-dead blarney from Killarney.


Yes, there is a correlation of mV to ppm of ozone – and other oxidizers such as chlorine and bromine. The basis for this voltage comes from chemical redox (reduction–oxidation) reaction equations. There is a specific formula showing the logarithmic relation of ORP voltage to ppm of oxidizers including ozone at  (STP: 25C @ one bar). The formula was in a specification manual for an ORP tester.  I’ve not found it online (yet).


The formula is interesting, but the problem is there are many factors that affect the voltage reading a probe may give. The pH is most prominent, but excessive organic matter (fish poo) can alter the readings too.  The natural chemistry of your aquarium will also affect the baseline reading. The best practice is to use this reading in conjunction with a separate test for residual ozone.  Once you know what is normal then you can adjust from there. 


I have two aquariums and the “normal” ORP reading is 420mV for one and 445mV for the other. A separate ozone test for both aquariums indicates 0.8 ppm to 0.9 ppm ozone.  This means the ozone is there and has the “potential” to do its job. If the voltage drops then the filters need attention or the ozonator is not working. 


Interestingly, even with these readings, both of the aquariums grow a slight amount of algae on the glass. This doesn’t hurt the fish, but it needs wiped off every few days because it obscures the view. 

 Oct 20, 2016

Cool beans! I didn’t ask the question but I have an aquarium and was considering if it might be worth buying an ORP tester.  What kind of fish do you have?

 Oct 22, 2016

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