ORP with water change

[flyingace2005]

I am just wondering exactly why my ORP drops drastically whenever I do a water change. I know that it's gotta be caused from the change water having low ORP but why does it have a low ORP and what can I do to make it even with the tank water? I do not run ozone on the tank and I run an airstone in my change water for a week.

[HighlandReefer]

I am no expert regarding ORP in the reef aquarium. It is a very complicated subject. ;)

I would not try to match ORP between your salt mix and your tank water. It will equalize out.

If the Orp in your salt mix is low then this means the reducers out number the oxidizers, simply put.

From Randy's article noted below these are some of the reducers that can cause your Orp in salt mix to drop:

"Reducers:

Metals: Fe++ (iron), Mn++ (manganese), many others

Most organics, especially "antioxidants" like vitamin C

Inorganics: I- (iodide), S-- (sulfide), NO2- (nitrite), NH3 (ammonia)"

Some salt mixes have organics like vitamins added to the the mix which may cause this. Salt mixes are known to contain some ammonia as well.

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

[HighlandReefer]

I would also add for your knowledge Randy's final statement regarding ORP in the Reef Aquarium from the above noted link:

"Recommendations for ORP

ORP is an interesting, if complicated, measure of the properties of water in a marine aquarium. It has uses in monitoring certain events in aquaria that impact ORP but may be otherwise hard to detect. These events could include immediate deaths of organisms, as well as long term increases in the levels of organic materials. Aquarists that are monitoring ORP in an aquarium, and are doing things that otherwise seem appropriate for maintaining an aquarium (such as increasing aeration, skimming, use of carbon, etc.) may find monitoring ORP to be a useful way to see progress.

ORP measurements are very susceptible to errors. Aquarists are strongly cautioned to not overemphasize absolute ORP readings, especially if they have not recently calibrated their ORP probe. Rather, the most useful ways of using ORP involve looking at changes in measured ORP.

Some aquarists use oxidizers to raise ORP. Those additions may be of benefit in some aquaria, and they may be beneficial in ways that aren't demonstrated by changes in ORP alone. I've never added such materials to my aquarium. In the absence of convincing data otherwise, such additions seem to me to have more potential risk than is justified by the demonstrated and hypothesized benefits."

[bertoni]

A lot of people report ORP drops with water changes, and don't have any bad effects. I wouldn't worry much. What brand of salt are you using?