Just an update about the Harbor Freight TDS meter now that I've got it and used it. It seems to be a reasonably nice pen type meter with temp compensation but non-replaceable probes. It also seems to give me repeatable readings but I've only used it a few times in different tap/distilled/spring waters.
The big negative - it only goes to 999 ppm so it's not usable with the G.H. Maxi
nutrients I'm using since they start off at 1300+ ppm. :-(
Since they call it a "Water Purity" tester I suppose I should have guessed there would be a catch, eh? :-)