Question about ORP

[SaltwaterKid]

I have an ORP probe on my AquaController and i honestly don't know what ORP is. What should it be at and when should i worry about it? Since my tank is very new, the ORP seems to stay in the 300's.

[JohnL]

This should get you started http://acmepet.petsmart.com/fish/mfira/13.html

[Randy Holmes-Farley]

ORP is a measure of the oxidizing and reducing properties of the tank, just as pH is a measure of the acid and base properties.

The higher the ORP, the more oxidizing is the water.

Few people do much with ORP any more. Albert Thiel was a big proponent of it, and selling his additives to raise it, but it isn't very popular any more. I do not agree with his assertion that low ORP means "dirty" water. I haven't measured the ORP of my tank for years.

When people dumped ozone into their tanks, they often monitored the ORP to ensure that they didn't overdo it. This is a good use of ORP, IMO, but the ozone isn't a good idea (or at least unnecessary).

Another thing that people did use it for was to alert the aquarist if a big animal died. In that case, ORP typically goes down.

I am reluctant to suggest an ORP value as optimal because I just don't think there is such a thing for our tanks.

Unfortuantely, i've not seen any good articles on ORP for hobbyists.