R u dosing continuously? If your using limewater continuously and having your fuge lit 24/7 then you should see less pH swings. And when you aerated the water you still got a ph of 7.88, not 8. To be using limewater and a lit fuge and still have such a high CO2 (pH and alk readings far off from each other) and such a large swing because of the CO2 puzzles me. I would still recheck the measuring equipment just in case.
What salt you using?
David - What buffers were you reading about? I just switched to red sea.
Yes, I was dosing continuously.
So I recalibrated my PH probes and there was no change at all. (well .05, but basically nothing). I then rethought my testing using the lamotte alk test. It is kinda tough to tell exactly when it switches from blue to purple. There's a bit of "grey" area.... So when I redid the test and used the lowest level of purple I saw, I came up with 110 ppm or about 6.0 dKH. These seems like the most logical conclusion to me given that my PH is so low and swinging quite a bit. I'm going to slowly add some baked baking soda liquid to the tank and get the alk up to around 9.0. Hopefully this will keep the PH more in line.
So far I've raised it to 7.0 and the PH has gone from 8.0 (at its highest when the lights have been on the longest) to 8.1.
Thanks for the help guys,
Nate