Water!
Re - the Hanna checkers -- yeah the Alkalinity one was such a huge win, I thought ... can't go wrong with also getting a Calcium checker! Yay me! .... Then I went to use it.
Hanna engineers in the different product divisions really need to compare notes more often.
(Don't get me wrong I still choose to use the Ca checker but compared to the Alk it's a total "WTF were you guys thinking?" moment. "Now add one nanogram of tank water to the vial..." ok ok maybe it's not THAT bad but it's close. Also you need lab grade distilled water. I've been using RO/DI instead, how ghetto!)
Glad to see water. It's such a moment of triumph isn't it!!