Apex with Orp: what's your readings?

[Michael43]

Mine does a little dip during the day and comes back up. My range is generally 400-440. Supplied my graph from the last few days via apex. The big dip low was the water change. I don't know much about orp but curious if mine are close to everyone else's.

 

[twilliard]

Here is one of Randy's articles
http://www.reefkeeping.com/issues/2003-12/rhf/feature/