Bill is correct. I need the YSI for my business. The ODO reads a lot faster than the membrane units, and when I am hauling fish I can't wait 15 minutes for it to stabilize before I start using it. If I did, it would add at least an hour, maybe more to each daily trip. Yes, they are expensive, but it has paid for itself many times over.

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).