I am stoked with my Bluelab Truncheon TDS meter and wonder how I managed to grow a hydro crop successfully before without it. Previously I have just used a pH meter in a recirc system (perlite) and just winged it without really knowing what was going on salt wise in my system. This tool has really boosted my confidence and would have to be my best investment. So I was wondering what growers sight as their best growing investment indoor or outdoor. Cheers Pat.