+1 on whatever your system holds up with. Water change advice runs the gamut. When I had a 2.5 pico I was changing ~0.5 gallons a day for 100% turnover per week, on my 90 I change three gallons 2-3 times weekly. My readings are fine this way, but I'm pretty lightly stocked. If you're heavily stocked you may want more changes.
And I do my changes in the evening, generally, to avoid hangovers
