Low PH levels in RO water

[jfenton954]

I'm having trouble with my PH levels droping in my 75 gallon reef tank around 7.86 to 7.56. I tested my RO water and the levels are low in that its in the 6.50 range. So when I do a water change in my tank it doesn't raise the PH. What could I use in the RO water to raise the PH?

 

[Anonymous]

are you airating the replacement water prior to you water change? simply running an air pump/air stone for an hour or two before performing the water change should raise it up to 8 - (.15-.44 isnt a big deficiency)

 

[jfenton954]

Thanks........ I will give that a try.

 

[Anonymous]

I add buffer to my resevoir.It also accounts for regular biological Alk depletion and keeps the pH up.

 

[AZDesertRat]

You cannot accurately measure the pH of RO or RO/DI water since they have too few ions to measure.
In reality it will be basically neutral and quickly take on the pH of whatever it is added to or is added to it.

 

[Anonymous]

You cannot accurately measure the pH of RO or RO/DI water since they have too few ions to measure.
In reality it will be basically neutral and quickly take on the pH of whatever it is added to or is added to it.

Seriously? How is it, then, that I am able to very accurately and reliably test not only pH, but also uS (microSeimens) of my own RO/DI water? By the by, the pH almost never comes out at 7. Any idea why?

 

[AZDesertRat]

You will never get an accurate pH of RO/DI water. Since the RO/DI is very agressive, meaning it is always trying to get back to its natural "dirty" state and is attracting anything it can from the container, the air, dirty hands or the TDS meter probe, anything. The pH of the RO/DI is really irrelevant since you are probably reading the CO2 in the surrounding air as much as anything.
Yes you can measure conductivity, resistivity or TDS as they are a measure of all things electrically conductive in the water. Again these readings will change as the water is stored or exposed to atmosphere and attracts contaminants.

 

[Anonymous]

Ditto. I would not bother with pH value in ultrapure water. It is does not make any use. The conductivity and other electrochemical properties is *specifically* derived to measure ultrapure water, and this is why you can get good measurement with the technique. With CO2 purging, you can get the conductivity of water down to 0.05 uS/cm. pH is related to dynamic of the chemical potential of the H+ ion. Since there are very few ion in the ultrapure water, the instrument will give you result that does not make sense.

BTW, "pure" water has pH of 7 under very specific conditions (temp for example). That assume there is enough ions in there for the measurement. It is very unlikely that one get 7.0 pH. If you buy a calibration fluid for pH meter, they don't give you "pure" water for a reason even if you get one at pH of 7. It is usually buffered with chemicals, for example.

 

[Anonymous]

Good stuff here 8)