Sup guys, got a couple of questions Is this Hanna Combo any good??? And also do you Need EC or TDS?(for DWC) i'm a little confused with which one is the one you need the most They got a TDS meter for $18 at bottom of page, will that work better than the Hanna? http://www.sunstoneherbals.com/hanna_combo_ph_ec_tds_temp_waterproof_tester_hi98129.htm