One thing I noticed this morning with the different flow profile at night is the pH dipped lower than usual. As you can see from this graph, the pH dipped lower than normal. (The "V" shape from the night before was the result of me manually turning the lights on earlier than usual. The pH dip on the first day in the graph was from a water change.) I think the lowered pH makes sense as gas exchange is lower when the flow is lower in the tank...this builds up more CO2 and lowers pH.
I'll have to keep an eye on pH and whether this seems to have a negative impact on the system. My thoughts for doing this initially was to make the tank a little quieter at night...that and just playing with WXM module. It may be interesting to try a lower flow during the day and higher at night to minimize the pH swings from day to night.
That's quite a drop from just a 20% reduced in ReefCrest. I'd watch it for a few days to make sure it's from your pump profiles and not some other interaction (dosing change, ambient CO2 levels...). I do agree those are large diurnal swings and <~7.6 is not ideal.
The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man. - George Bernard Shaw