Excessive indoor Co2

[Andrew]

Ok,
I definitely have a bad problem with too much Co2 in my house.

For the millionth time, I confirmed it this weekend, Fri, Sat, Sun were cool enough to open the windows and turn off the AC.
Before I opened my windows I cleaned out my Top-off reservoir and filled it straight RO/DI instead of my heavy duty Kalkwater.
By mid day Friday the pH was up to 8.05, by evening 8.15. My pH never dropped below 8.0 the entire weekend.
Just an FYI: If I had left my top-off reservoir filled with my kalkwater, the pH would have shot up to about 8.9. (past experience)
Sunday night I closed the windows and turned the AC back on in anticipation of the warmer weather heading in.
I get up Monday morning to see the pH of 7.6....uuuggghhh....the usual morning low. I forgot to switch my top-off water back to kalkwater, so my pH never got over 7.7 the entire day. My usual high pH reading is about 7.93, with lows around 7.56.

My pH monitor is brand new, and is calibrated. I even checked it out with the twenty mule team mixture. My old one was acting kind of funny, so I replaced it.

I have done and am doing everything to correct this problem, but it isn't going away.
I have my skimmer's air-line ran thru a wall to the exterior of my house to get outside air.
I dose a kalkwater mixture of 4 tablespoons per gallon, in my auto-top off reservoir. I only make 2.5 gallons at a time, and I evaporate about one gallon a day.
My mixture to increase Alk raises the pH, but it just slowly falls back down or drops a little and then stays steady.

My pH never gets above 8.00, unless I turn off the AC and open all the windows in the house. Just opening the window in the room the tank is located is not enough.

Now, finally on to my questions........(sorry so long)
What long term affects will this have on my corals?
Does anyone have any suggestions for correcting the problem?

I am starting to think about just taking down the tank, because I can't get the pH to be consistant or at the correct level. Tank was up for 2 years as a 20g, with a solidified aragonite substrate, then I dumped everything in a 40 breeder, same equipment, more rock and a bare bottom and it has been set up for 8 months now. I had this pH problem since day one in my 20g, but recently the numbers seem to keep getting lower. I was able to keep my lows to about 7.8 and my highs about 8.05 with the 20g during winter and summer.

My pH problem is seasonal too, only happens in winter and summer, fall and spring is cool enough to have the windows opened.

See Andrew's tank under the Tank Spec section for further info.
(for some reason I can't paste a link here because I am using Mozilla?)

I thank everyone who took the time to read my ramblings....LOL

[rabeiler]

Andrew,

I know just how you feel. I have the same issue with my 120g. I have been able to stabilize my at around 7.9 to 8.0, but it only goes above the 8.1 range when the house is opened up.

My tank is built into the wall with a small fish room 6 feet by 14 feet. I have to keep the door open to help with the PH issue when the house is closed up. Here are a couple of the things that I have done beyond what you have done.

1) Have several fans running at top of tank to keep air moving. Run these 24 hours a day.

2) I have an bathroom exhaust fan suck expel air outside.

3) I run a refugium to help consume excess co2.

4) I use a Nilsen reactor for makeup water.

So far I have not had a long term ill affects.

Ross