It will be interesting to see results on DOC as more people start to use N-DOC testing, unfortunately I have little faith in triton over this as they won’t fully explain there conclusions or share the data they based it on, here’s a link to their “technical” paper, they refuse to answer any questions on there methodology at all, be interested on your thoughts Dana.I guess having high DOC in an aquarium is possible, but I've performed the Five-day Biochemical Oxygen Demand test a number of times. These were performed in accordance with EPA-approved methods (incubation in darkness for 120 hours at 20C, and used either a polarographic or one of the newer luminescent dissolved oxygen probes. These were 'straight' samples with no dilution - a full 30 milliliters was used.) For the test to be valid, there has to be a drop of at least 2 ppm dissolved oxygen but the most I ever saw was 0.2 ppm. These samples were spiked with a chemical that inhibits nitrification, thus they are reported as Carbonaceous Oxygen Demand. I wasn't dosing any carbon source (methanol, vodka, carbon-based additive, etc.) so it is possible that some aquaria have high levels of organic carbon, I just haven't personally seen one.