Regarding changes, I sometimes let my tanks go down 1-2, even 3 inches, leave it like that for a few days, and then finish the waterchange with cooler water. I'm probably overthinking it since they're fish, but I imagine it would be similar to being a period of drought and then a large rainstorm that washes out most of the remaining water and replaces it with cooler, fresher water. Dunno, but the fish seem to like it haha.