I guess I'm having trouble understanding why your tank ph is a constant 7.0. If you inject CO2 your ph would drop during those hours unless you aren't adding enough of course. The water that you started the tank with...wasn't that your tap water (at 7.6)? What I'm getting at is that if your tank ph is naturally 7.6 and CO2 is bringing it down to 7.0 then that ph swing shouldn't have any effect on your fish. On the other hand, if you tank ph is 7.0 because of some other reason then yes, there might be some stress with changing ph too abruptly. A 10% change of water would have only a small amount of shift or even 20% for that matter. Try that and keep an eye on the fishes.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.