Redox in a new tank?

[jdjeff58]

I'm in the process of cycling a new tank. I'm about 3 weeks into the cycle with live cured rock. I never saw any ammonia or nitrites. My nitrates went up from 2.5 to 5 after adding a raw shrimp and have been holding at 5 ever since. I'm being told that it looks like my cycle is complete and to do a 30% water change.

My pH has been holding relatively steady at 7.9-8.0

Along with my new tank, I bought a profilux controller. I'm monitoring pH, conduct., temp....and now redox. The ph, cond., and temp probes have been up and running since the beginning. I also have a redox probe and just decided to calibrate it last night....initial calibration. I had no special reason for waiting, other than to do some reading on redox before I put it into operation.

After calibrating with 220mV solution, I placed the probe in the sump. Readings began to slowly drift downward until they bottomed out at around 136mV. Approx. 12 hours later the readings have drifted back up to 184mV. From what I've been reading, these readings are relatively low.

Out of 4 or 5 articles I read on redox, there was only a couple of instances where they mentioned low readings after calibration...allow 24 hours for probe to settle in. But none of them seemed to mention redox in an unestablished tank. Would low numbers like mine be expected in an unestablished tank?

I'm just trying to get a handle on what I'm seeing here. Any help would be appreciated.

[bertoni]

This article covers the basics of ORP:

http://www.reefkeeping.com/issues/20...ture/index.php

I would just ignore the ORP readings in this situation. There likely is still a lot of decay ongoing, and ORP is hard to interpret in any case.

[jdjeff58]

Originally posted by bertoni
This article covers the basics of ORP:

http://reefkeeping.com/issues/2003-...ature/index.htm

I would just ignore the ORP readings in this situation. There likely is still a lot of decay ongoing, and ORP is hard to interpret in any case.

That link is not working for some reason.

[bertoni]

Sorry, I cut and pasted it incorrectly. Fixed.

[jdjeff58]

Originally posted by bertoni
This article covers the basics of ORP:

http://www.reefkeeping.com/issues/20...ture/index.php

I would just ignore the ORP readings in this situation. There likely is still a lot of decay ongoing, and ORP is hard to interpret in any case.

Thanks bertoni...I just read over that articles again...I think that is about the third time I read it. I really didn't see anything that discussed a new tank in there either.

I'll just have to keep an eye on it and watch what happens after water changes and the addition of some chaeto in my fuge. I'm getting ready to do my first water change 30%.

I understand that there is not an ideal ORP value. And it is just an indication of something going awry when it goes down. But all the articles I've seen do say there is such a thing as too low and too high. <300mV and >500mV is supposed to be bad. I guess I'll have to assume that is in an established tank.

I also read that it is not a bad idea to watch your cycle using a redox probe. The only problem is that I didn't comission the probe until now.

Since the last post it has crept up to 194mV. So maybe it's just a probe settling in issue combined with a new tank.

[bertoni]

Many organic compounds are reducers, and during the initial curing phase, the organic content of the water might be very high. It also might be a probe issue.