I agree about the soap, also try to purchase test kits, because like that you can go by something other than a LFS person telling you a vague answer like "your water is fine"
hmmmmmmmmmmmmmmmmmmmmmmmmmmi had my minnows in a jar, which was a ecosystem that provided the essentials and basics to them for the 10 days. than i opened the jar, after the ten days and put the fish into a new jar that was clean and everything, temporayliy, until i found them a tank. And then after a couple day i moved them into the tank, after it had settled. also, i had made sure that both jars, provided the fish enough room to swim freely.
The white residue was most likely just hard water stains which could have been removed with regular old household vinegar (which btw would have been safer). On a tank that has been fully set-up don't use any kind of cleaning products...an (unused) toothbrush or algae scrubber will remove most things on the glass / decorations. Gravel vac all the substrate at least once per week, and the only chemical you should ever put in your water is a water conditioner like Prime to remove chlorine/chloramines.that by using biodegradable soap it'll help clear up the white residue from that was previously there.