pH Fluctuations

[mediaone]

Of those of you with calcium reactors, what is your pH fluctuation from its low point at night to its hight point during the day?

Do you feel that the large amount of CO2 used (especially in older tanks) to maintain calcium and alk levels via reactors is having too much of an impact on pH? Maybe older tanks start to crash because of this pH fluctuation from night to day; given the tank is using a calcium reactor.