Internet DO Charts don’t lie and real DO Test don’t lie, but the charts and test are seriously conflicting. The internet DO charts do not jive with the actual DO test results which I found was nothing like the DO chart predicts and absolutely shocking, but true and correct after 10 different DO test. The DO chart prediction and the actual DO test were all very different 100% of the time. If you believe the DO chart prediction is what’s happening in your DWC cannabis grow, well, you are in for a major disappointment and real enlightenment. I doubt that anyone of a cannabis forum ever tested DO in a DWC grow. And who would ever question the actual DO hydroponic DWC grow vs. the internet DO chart prediction and forecast. Clearly, the only way to discover the real deal is to test the DO so I bit the bullet and actually tested the DO. Of course I did not buy a $100 DO meter, but I did buy a Salifert Dissolved Oxygen Test Kit which was in line with my test equipment budget. This DO test kit contains 50 test strips, cost $22.31 and shipping was free. Each test cost $0.50 which is reasonable in my opinion. https://www.amazon.com/Salifert-Dissolved-Oxygen-Test-Kit/dp/B001EJ3DQ4 My pH meter cost $150, but it is a good one and worth the money. The DWC forum gurus claim you got to have 100% DO Saturation in reservoir to prevent the “low oxygen problems” like preventing roots from suffocation and Pythium outbreaks which all sounds logical to me. They also say you must have a water chiller to insure plenty dissolved oxygen, nothing else does the job. They say fungi thrive in low oxygen environments and oxygen rich environments (DWC reservoir water) promotes excellent root and aerobic microbial health. DWC gurus claim that oxygen rich reservoir environments play a major roll preventing fungal outbreaks and disease infestations. Here’s what I discovered this discovery was totally unexpected, shocking! DO chart prediction at sea level, fresh water, NO aerobic plants/microbes in the water consuming Dissolved oxygen no aerobic metabolic processes going on in water DO Chart Prediction: 80 F water temp DO concentration 8.0 PPM DO DO Saturation 100% Real time DO Test in reservoir water containing mature cannabis roots and Great White beneficial microbes (1/2/ gallon or 4 lbs.) DO Tested: 80 F water temp = DO 4.1 PPM DO Saturation 51% _______________________________________________________________________________ DO chart prediction at sea level, fresh water, aerobic plants/microbes living in the water consuming dissolved oxygen necessary for aerobic metabolism DO Chart Prediction: 70 F water temp DO concentration 9.0 PPM DO DO Saturation 100% Real time DO Test in reservoir water containing mature cannabis roots and Great White beneficial microbes (1/2/ gallon or 4 lbs.) DO Tested: 70 F water temp = DO 4.8 PPM DO Saturation 53% The DO chart predictions and the DO Test do not jive Why? So where did all the dissolved oxygen go? Keep this in mind the next time a water chiller sales shows you a DO Chart justifying the necessity of buying a $400 water chiller. Test the DO and see the difference. I can see now why there are many growers that look at their DO chart and cannot understand why they have caught the Pythium fungal disease. The Question I have for you DWC cannabis growers is: Do you have any idea “what happened to all the dissolved oxygen in the DWC cannabis grow?” The dissolved oxygen certainly did not off-gas nor evaporate into the air.