I've recently upgraded the lighting on my 10g tank in an effort to improve the growth of my plants. I went from a single 15w T8 to 39w of CF lighting. I also started shutting off the aeration during the day to let the CO2 buildup for the plants.
All seemed to be going well, the plants were pearling, the fish were happy until I did the weekly water tests. Everything was normal, until I got to pH. Our tank has been at a steady 7.8 for two years, a little higher than the tap water (7.5), but we have some limestone in our gravel (bad batch ... )
Last sunday it was at 8.6+, off the charts of our pH test.
We checked it three times, checked the test (it's reacting properly) and re-checked the tap water (7.5, like normal). The test was done in the evening, after a whole day with no aeration.
To make the story even more strange, we re-checked the next morning, after aerating the tank all night, and .... pH=7.8.
Turned off the aeration for the day. Just for the fun of it, I check at around noon, pH=8.2, but days end it's back to 8.6+. This with the aeration turned off.
I though aeration was supposed to increase pH, not decrease it? And that letting CO2 buildup is supposed to bring it down?
Our tank is apparently working backwards. The only explanation I can think of is that the plants are stripping out all the CO2 and the pH is going up ... but frankly I'm grasping at straws.
So what do you guys think is going on in my tank?