Using ORP to measure interesting things in Tank Water

[taricha]

I think this experiment will be difficult to interpret because a protein will have lower reactivity to chlorine ((as hypochlorite/hypochlorous acid) than the component amino acids if present as individual amino acids.

(I hadn't run across the second link. nice, thanks)

Yep.
Hence, I can measure that amino acid standards need roughly 5 or 6 times as much Cl2 as equal mass of protein standards, though they are made of the same stuff.

And your point is why I can measure that a day of aerating a bottle of my tank water with GAC reduces the Cl2 needed by ~2ppm (from ~3.5 ppm down to ~1.5ppm Cl2) - but I can't say what that N / organic material is!
That ~2ppm Cl2 consumption could be:
~0.4 ppm ammonia (it's not - ammonia test rules it out down to 0.02 or so.)
or
~2.2 ppm of amino acid
or
~10 ppm protein (seems too high to be likely)


Attempting to correlate with a Triton DON measure might be fun and illuminating.