# Airstone increase ph?



## Axelrod12 (Jun 28, 2013)

Nope airstones should have no effect on ph. They just improve water movement and gas exchange. If your injecting co2 it will off gas co2 much faster.


----------



## FungusTrooper (Jul 8, 2013)

Ours becomes more base as water oxidization increases. When we fill a bucket with tap water, it is a perfect 7, but it usually gets nearly to 8 overnight as the airstone oxides it.

To test yours, fill two small buckets/cups/whatever with tap water. PH test them in the evening, then put an airstone in one overnight, then test them both in the morning. Your PH will probably have changed in the one with the stone.

But, again, it isn't the stone itself, merely the act of oxidizing the water.


----------



## ngrubich (Nov 29, 2011)

FungusTrooper said:


> Ours becomes more base as water oxidization increases. When we fill a bucket with tap water, it is a perfect 7, but it usually gets nearly to 8 overnight as the airstone oxides it.
> 
> To test yours, fill two small buckets/cups/whatever with tap water. PH test them in the evening, then put an airstone in one overnight, then test them both in the morning. Your PH will probably have changed in the one with the stone.
> 
> But, again, it isn't the stone itself, merely the act of oxidizing the water.


??? Oxidation of water ??? The half-reaction of water oxidation that involves the oxidation step produces H+, not OH-. Even then, there isn't any electrical current (or catalyst depending on the type of water oxidation) being passed through the bucket of water to drive the oxidation of water.

The main reason why the pH of water changes overnight is due to CO2 gassing off. That process is accelerated by adding an airstone.


----------



## jeepguy (Jul 24, 2013)

No matter what from what I just learned yes. An air stone will increase the ph the same way co2 injections decreases the ph. But, the kh and tds do not change, which are the numbers that fish actually care about.
Are you trying to make your ph higher?
The sponge filter if run by an air pump will increase the ph slightly as well by offgasing more co2. 
But it doesn't matter anyway unless you are planning on injecting co2.


----------



## amphirion (Nov 13, 2008)

if pure water we're talking about, then the pH difference between adding an airstone or not will be negligible. however, carbonates have the potential to alter water chemistry if their equilibrium points are saturated.

Prior to Airstone:
H2O + CO2 <--> H2CO3;
H2CO3 <--> H+ + HCO3-;
HCO3- <--> H+ + CO3-2;
so total net: H2O+ CO2 <--> 2H+ + CO3-2; (acidic).

as others have stated adding an air stone allows off gassing of CO2, so the equilibrium begins to shift to the reverse set equations mentioned above, ie if there isnt enough CO2 present in the system, the CO3-2 begins to convert itself back into HCO3-, then H2CO3, then H2O and CO2. as you can see, the 2H+ that we originally had released are consumed back into the system and so the pH increases. now if we had even more carbonates in the system than the balanced equation, the swings between low and high pH will be even greater as protons will be in even more demand since every free proton created from bicarbonate dissociation and hydronium will be consumed. so it is possible for pH to go from 7-8 overnight with an airstone. pure water's supposed to stick around somewhere between 6.8-6.8 if i recall correctly.

i hope i explained that right...


----------



## BBXB (Sep 18, 2013)

I currently do not inject co2. I just want to add airstone for my shrimp tank but don't want ph to rise.:redface:


----------



## Axelrod12 (Jun 28, 2013)

Interesting I've never heard of an airstone changing ph significantly besides the slight swing of offgassing co2. Never thought that increased carbonates would have a significant effect. I'm gonna do a test on a couple buckets of tap tonight to see what happens with our water.


----------

