Ok made my first big batch of tea(50 gal) with my homemade brewer, looks a little on the light side biology wise. SO, what is a good DO meter to buy for starting out, and or which one should I save up for? Where to purchase from? Are the ysi 58 that are all over ebay for like $100 worth it or should I get a new one with a warranty? Hopefully Tim will chime in on this one, Thanks everyone.