PH control with CO2

[nycman]

I have a large tank 200G with overflow and sump. After several tweaks on the plumbing, I have virtually no surface agitation and ability to overdose on CO2 (based on my history with this tank, a good thing). I am getting Discus and want to be more careful with the daily PH swings. I run the CO2 8 hours a day inside of a 10 hour lighting period. Without the PH controller, my PH would peak at 7 (my tap water PH) just before the CO2 would come back on, and then during the 8 hour CO2 cycle dip to upper 5 or lower 6, depending on my bubble count tweaks.

Here is my question on setting up my controller...with Discus, should I:

1) run my CO2 24 hours a day with the controller auto shutting it on and targeting a specific PH - I have tested it and can keep it very stable at 6.3 to 6.5, and still get ample CO2 into the tank. This way the PH of the tank will be at this value 24x7 as I will be running the CO2 at night as needed for this PH.

2) run it on the 10 hour lighting cycle, shutting it off at night and allowing the PH to creep back up to 6.8 or 7. This way the daily PH fluctuation will be 6.3 or 6.5 to 6.8 or 7, not insignificant, but not huge.

Assuming both approaches are equally appropriate for the plants - which is better for the Discus?

[Hollowman]

Stability for Discus