Interesting! After loading up the UNS with media, I added a small powerhead (Hydor Koralia 240gph) to the 90L/20g long to compensate for reduced flow, as that seemed to be a likely factor in algae issues. I had been trying to pay attention to this in putting the scape together, but hadn't quite anticipated how tricky flow could be.
Doing water changes (tap water) this weekend, I had just been thinking that a spot thermometer would be really handy. I tend to go by touch, and inevitably worry about the variation. I suspect your amanos are going to be able to handle a little bit of GH change though, they're very hardy shrimp. Still, if you enjoy the precise measurement of things, this could all be good training should you wish to introduce some more sensitive shrimp down the line.