I watch my ph swing everyday. It was going from 7.75 to 8.2 when my doors and windows are closed. I ran my skimmer line outside and not its 7.9 to 8.3. When the mornings are cooler than 70 I open the front and back doors at 6 am when I leave for work. My girlfriend close them at 8:30. This makes a huge difference. I can watch ph go from 7.9 to 8.1 in 3 hours while the tank lights are still off. I have a refuguim on reverse light cycle which also helps. What I'm wondering is if anyone has ever experimented with putting a bunch of plants in their fish room. I'm thinking a few large ferns. They would love the humidity and the light. I just wonder if it would make a difference. With winter coming I won't be able to open up house for 2 or 3 hours everyday.