Question about PH

[Joboo]

Randy,
I have been dealing with a low PH problem (8.0 - 8.1). Well I guess its not that low but I would like to be more in the 8.2 range. I have been dosing lime but the problem is that my CA and ALK are at there high limits and I have to stop dosing for a few days. within those few days my PH starts to creep downward(8.0 - 7.95). I'm thinking that I have a CO2 problem and will be running a fresh air line to my skimmer within the next few days. However, I wanted to know if Salt can cause low ph?

Thanks
John

[Randy Holmes-Farley]

The nature of the salt mix doesn't impact the long term pH very much.

What values do you have for calcium and alkalinity?

[Joboo]

Randy,

ALK - 10.2 dkh
CA - 500ppm(this is using Aquarium Pharm Tetskit, 550ppm using Salifert)

Last Night I left a sliding glass door that is next to my Sump area open. My PH this morning (10 hours after) is still at 8.10. I will check tonight to see what the PH is at.

[Randy Holmes-Farley]

How are you measuring pH?

[Joboo]

AQ II lab grade probe. I have calibrated it about a week ago. Then yesterday I dropped it in some 7.0 fluid and 10.0 fluid with accurate results.

[Randy Holmes-Farley]

I'd suggest aerating a cup of your water with an airstone for an hour and see if the pH rises, or not.

Try that with both inside and outside air to see what happens.

[Joboo]

Thanks Randy. I'll let you know how it turns out.

[Randy Holmes-Farley]

:thumbsup:

[Joboo]

Ok, here is the update.

I have not done the aeration test yet. However, I had a 40g trash can brewing Fresh SW for a water change. The water parameters were as follows:

SG 1.025
PH 7.69
ALK 6 DKH
CA 540ppm


I had some CALMAX Two part additive that I purchased a while back and added part B(ALK) in the amount of 40ml(1ml per gallon = 2 dkh raise). Tested the water and PH was 8.15. As per your doc on PH one of the reasons you state for low PH is low ALK. Would this be the cause of my low PH?? Thx

[Randy Holmes-Farley]

No, that water has excess CO2 in it, assuming that the pH was measured correctly. Has it been aerated well?

This graph shows the relationship bewtween pH and alkalinity for water equilibrated with normal air (that is, no excess CO2):

The Relationship Between Alkalinity and pH.
http://www.advancedaquarist.com/issues/may2002/chem.htm

http://www.advancedaquarist.com/images/may2002/figure1.gif