Effect of lights ON and ORP

[cmoore806]

I have a one month old 40b with a single Radion XR15 Pro (will be adding the 2nd, not in a hurry). Dry rock, rinsed/washed sandbed. Sump with skimmer running. Up to this point, no animals in the tank, just dosed Dr Tim's, microbacter7, Microbacter CLEAN, and have used FaStart-M and ghost feeding to keep growing the biofilter. I decided to turn on my light now after a month of lights off. They turned on at 9am shown on the chart below.

So my primary question is why did the light getting turned on increase the ORP? I've read about ORP a fair amount and cant figure out how the lights are increasing the ORP.

Last Parameters:

Ammonia 0
NItrate 13.2ppm
Nitrite 10 ppb
Phosphate 0.04 ppm

 

[Randy Holmes-Farley Verified Community Expert]

Looks like maybe it was starting to rise before the lights came on, and maybe is just drifting. I'd watch it after lights out then light on next day to see any regular trend like in the article below.

Usually, ORP drops during daytime as the pH rises.

http://reefkeeping.com/issues/2003-12/rhf/feature/index.htm