the ones you leave in are expensive if you have the bucks. I use a sunleaves tds pen very easy to use and just got a milwakie ph pen. sorry about my spelling. It makes a great difference when you can just stick the pens in the water and get an accurate reading in seconds. Depends on how big a grow and res you are doing. hope this helps. at least it's a start.
LOC NAR1958 Reviewed by LOC NAR1958 on . pH/TDS meter Been growing in dirt for a while, using chem indicators for pH and TDS. Worked well. Grew last batch in a drip/bubbler hybrid frighteningly similar to one of the systems I saw on the board recently. Anyway, using the chem indicators is a bear but the hydro results were superior even on my first try. What brand are you guys/gals using? Combined meter, or separate? Any models that you can simply leave in the resevoir, or are they too delicate? Thanks Rating: 5