Never had trouble with pH before, but never had to deal with RO water, either. Apparently the little bit of gravel, maybe 1/2 pound, I added as decor is the prime suspect in the jump of my pH from 6.6 to 8.4. Most of it sealed off with the silicone I used to attach it and whatever coating TopFin uses to make it shiny. You can see all of the gravel from this angle. It is a single layer siliconed onto french drain piping The KH has gone from 6 dKH to 7 dKH, not enough to matter to me. Would so little gravel cause this shift? The only other change is the addition of plants but that should bring it down if anything, right? I can remove the gravel (substrate is EcoComplete) and redo the work with trap rock which, from what I am reading, is basalt and doesn't mess with the pH if the gravel I used is the culprit here. Your thoughts?