ORP measurments

Do you measure redox potential in your tanks?

If so, what equipment do you use, who makes good calibration
fluids are proven the best and what are your readings?

I have read a little about this ORP and it is recommended
as a quick check of helth status of your tank water...
Lower the ORP potential the more dissolved organics
and less oxigen for animals... They say it is necessary
measurment/control if you dose ozone or hydrogen peroxide
- they both rise ORP quite rapidly and without measuring
you are running a risk of overdosing...

Do you have your own experience to share with the group?