why's my pH so low??

[Beverly]

Reef chemistry links that might be of interest to you:

Aquarium System Volume Calculator:

http://home.comcast.net/~jdieck1/volcalc.html

The Reef Chemistry Calculator:

http://home.comcast.net/~jdieck1/chem_calc3.html

Reef Aquarium Water Parameters:

http://reefkeeping.com/issues/2004-05/rhf/index.htm

Magnesium in Reef Aquaria:

http://www.advancedaquarist.com/issues/oct2003/chem.htm

Solving Calcium and Alkalinity Problems:

http://www.advancedaquarist.com/issues/nov2002/chem.htm

HTH

[danny zubot]

Ca-490 ppm (no supplimentation)
KH-9.3
SG-1.025 (too high?)
pH morning-7.8 evening 8.0
no3 and po4 barely perceptible
added another power head for surface circulation

Calcium is a tad on the high side but that will correct naturally.
KH of 9.3 equals 2.65 Meq/L Alkalinity, dead on.
PH is on the low side of normal but acceptable. What kind of substrate do you have? Aragonite and live rock should bring your PH up a bit and act as a Ph buffer.

[Beverly]

Another thought occurred to me. We don't have any fresh air coming into our condo unless we open windows. In winter low pH was especially a problem, until we began to open our bedroom windows a crack and have a floor fan blow the fresh air into the living/dining/tank rooms. Do you have fresh air coming into your tank room? If not, high CO2 in the air could be a cause of your low pH.