How useful, interesting and/or educational would a Dissolved Oxygen (DO) meter be toward learning and understanding planted tanks be? Or even for keeping killies, or anything else? This came up as I was reading a book on South American Dwarf Cichlids and every once in awhile there is a listing in a table for a specific species listing DO as milligrams per liter (mg/L) and that got me thinking about: (a) how is DO measured electronically; (b) what can it tell or indicate to us?

I still have some of my "economic stimulus" check left and came across the Milwaukee SM600 DO meter for ~$175 and was intrigued.

(I already have a PAR and pH/EC/TDS meter, and am experimenting with them.)

-Jason