[quote author=Ibn link=topic=2460.msg25374#msg25374 date=1191360240]
The way that I understand it is that pH rises as carbon dioxide is depleted. The converse also holds, pH drops as carbon dioxide builds up. Corals and plants carry out photosynthesis throughout the day, producing oxygen and depleting co2. So as the light cycle continues throughout the day, pH rises.
Aerating the water drives off any excess carbon dioxide and absorbs carbon dioxide when deficient, preventing the pH from swinging. According to Randy Holmes-Farley, pH usually doesn't rise beyond 8.5. If it does, it's probably caused by lack of aeration and aerating the water will solve the issue.
When the tank is lighted, even with low flow, you'll get a high pH, as co2 is being depleted. At night, you will get a low pH since co2 builds up.
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Yeah,That's right.Lights on in tank ph goes up 2-3 pt. I also thought it was too much CO2 in my room but I ran a fan still the same after a few days.Let me check on the ALk again. I think I can pinpoint when it started.I add a denirater and my PH started to drop about 1-2 weeks after that.I have since removed it for about 2weeks.