I don't know what you're talking about - nothing in that thread contradicts what I'm saying.this has been stated previously, @Randy Holmes-Farley posted this...
https://www.reef2reef.com/threads/hanna-salinity-tester-first-impressions.539986/page-4
The primary reason people have issues with the Hanna salinity checker is the same reason people get weird readings out of the Apex salinity probes - its because they measure conductivity - and use it as a proxy for salinity - but there are things in a reef tank that can affect salinity.
I'm not talking about contaminants (like Randy is refuting) - I'm talking about pumps and heaters and uv sterilizers and all sorts of other things that induce transient current in salt water.
Some tanks you can stick a conductivity probe in the tank and get one reading, transfer some water to a cup - and get a very different reading.
