my 55 has co2 and is high tech
my 29 has no co2 and very lightly dosed with ferts
i assure you that the pearling with water changes is very common. and i'm sure that your pearling has everything to do with the water change. it happens in my 29.
You are right I let a glass of water from the same water source out for a couple of hours and there were bubbles all over the sides. So I guess it has more stored gas than I thought.
I was kind of hoping I was going to find something in the water. At least I got to the bottom of it though.