saltwater ORP

[jer77]

Hi, I was wondering what would be the cause of the RO/DI water and the saltwater make up water ORP being low? If its anything to worry about at all? Its around 180mV. I'm thinking the water may be causing my tank water to be a little low because I keep replacing it with it. Thanks.

[Randy Holmes-Farley]

That is not unusual and not a cause for concern. ORP should not be something that you are targeting per se. In a salt mix, it may just mean that there is more ferrous iron then ferric iron.

This article has all you need to know about ORP:

ORP and the Reef Aquarium
http://reefkeeping.com/issues/2003-12/rhf/feature/index.htm