I have recently come across a few mentions of redox and the impact on fish health. ORP measurements seem prevalent with reef keepers but there was a suggestion that it was equally useful for freshwater. (exactly how was unclear and I guess this is a bit like TDS and probably more likely to cause confusion than actually help anything?) I guess the question I have is whether redox is actually important? This is a proxy for BOD so presumably it would be an indication of a build of of organic waste or overstocking? I see that ORP meters are pretty expensive but if they were the same price as pH pens and also accurate would we all be using them?