HI & welcome to AA.
I am not too familiar with Redox potential <That is another name for ORP & is more commonly used by chemists here.> & its implication in FW
aquarium. I *think* this is more a SW
issue ... but you better ask the SW
gurus in the SW
side of the forums.
From a chemistry viewpoint, Red-ox potential is the ability of "tank water" (or other substance) to donate an electron (in a chemical reaction) ... or the ability to oxidize, although oxidization is only one of many ways to donate electron.
So bleach, H2O2 or potassium permanganate (to name a few things use in aquariums) all are oxidizers (ie they have positive Redox). Organic stuff collected in your tank are mostly reducers (negative redox, electron acceptors). The oxidizers have the ability to react with the reducers & neutralizing them. Thus you can add PP to your pond before you do major cleaning to neutralize the organic debris that you stirred up in the water. The oxidizing effect is what make these substance effective as disinfectant.
I suppose you can use redox in FW
as a measurement of your DOC
content. But the only thing I came across regarding redox & FW
is in discussion of UV
sterilizers ... they are supposed to improve redox (ie get rid of your dissolved organics) & improve fish health ..... no idea if this is really true or not, although some of my pond friends do swear by their UV