pH cycle...too high?

[untamed]

Its a two stage reactor, so it probably isn't affecting the tank as much as might be expected....and I'm only running the reactor at 6.8.

My Ca/Alk demand is such that I could turn the reactor up....based on the current pH, I think I'll drop the reactor pH a bit and see if that causes any affect upon it.

There is a good chance that the 48" x 72" surface area, as well as two sumps (18" x 36" & 24" x 48") might be contributing to better-than-usual gas exchange.

I also think that I can see the effect of glas cleaning in the daily fluctuation. When the glas is cleaned, the cycle is slightly lower. As the glas greens up, the cycle gets higher.