One thing that my signature generation program does is provide graphs of temp, ph, and ORP. Every so often I'll look at my graphs and see if I can notice any trends.
If my ph consistently drops, it usually means my alk is also dropping faster than my doser can compensate. If my ORP drops suddenly, it could mean something died in the tank (or there was a spawning event.)
I've seen folks ask the question, "Why does my ORP drop when I do a water change?", but I hadn't observed that phenomenon myself with my tanks-- until recently.
Here's a graph of the last 90 days of my ORP. Those seven steep drops correspond to water changes.
Thing is, if I look back at the time frame before this, I don't see the same drops in ORP.
The thing that changed? I switched from Seachem Reef to AquaVitro Salinity.
I don't plan on changing anything, this is just making me curious.