Okay I’ll look into this. I have a lid so I don’t do top-offs, per se. Or at least not much. I had been doing weekly water changes of around 20-some-odd percent for a long time and decided to be a little bold and daring and change my routine to every other week.* That said, there is always at least a small amount of evaporation.
And after writing this post, I realize there are a few sources of rocks - some aquarium-store-bought rocks (probably slate) and a small amount of Petco gravel.
But I’ll look into the video. Can’t right now. Thanks!