Q: MV (Redox potential) readings

Hi again fellow aquarists,

There has been talk about Redox potential and MV readings. what exactly is
Redox potential? (my high school chemistry was really bad) What does the MV
reading on an MV meter mean? Believe it or not, I actually do have an MV
meter on my tank now (brought over from the conversion of the reef tank). I
just know that for reef tanks, the higher the meter reads, the better is
your water quality. (I was a novice reef tanker together with my dad and as
you can tell, we obviously failed bad and decided to convert our old tank to
a planted FW one). Readings of 300 plus was considered good for marine reef
tanks. I get readings of 480 plus in the night and it goes up to some 500
plus in the day. Is this normal?

Why is it that we get much higher MV readings in Freshwater tanks than in
reef tanks?

still having an ozonizer and protein skimmer left over from the reef days.
Calvin Chin