Pond Boss Forums GENERAL QUESTIONS Product sources Thermometer

Dave - I checked out BassProShops Temperature-Oxygen meter. Yep. It is the same one that I described above. It doesn't really measure dissolved oxygen it estimates it and assumes perfect conditions at specific temeperatures.

"Reasonably priced (relatively cheap) DO meter".??
$225 minimum from Aquatic Eco-systems Inc. By Pinpoint. One could also routinely search on eBay. Occassionally good used ones show up, but plan to have it refurbished at the manufacturer to standardize or recalibrate the components. YSI has the highest reputation for DO meters.

Trouble with DO meters is they are relatively complex, sensitive and high maintenance. To measure dissolved oxygen in water, meters with probes require diss.oxygen to permeate through a membrane. The oxygen is reduced at a cathode and the resulting current is measured & converted to a readout. A counter reaction of oxidation of silver at the anode/reference electrode also occurs which completes the electrolytic reaction. This oxidation of silver tends to over time decrease the accuracy of the probe/meter. Thus DO meters/probes are high maintenance & expensive items.

If you only want to only periodically measure dissolved oxygen in the water and do it inexpensively you should use the chemical test method. It is relatively simple & quite cheap but a little time consuming. DO measuring chemcials are low maintenance and have a relatively long shelf life. From my experience the chemical method is frequently more accurate than meters as they are typically used. Many meters are not calibrated properly nor are they adequately maintained. Thus they often provide inaccurate readings unbeknownst to the nieve user. Many electronic meters are frequently negelected and they are never ready when they are really needed. Even the best DO meters need to go to the factory routinely for standard servicing & recalibration; as I said high maintenance items. My water chemistry professor and a limnological methods professor were both sticklers for calibaration and maintenance of instruments.