Low ORP     2/23/14
I have a new commercial reef setup.  It's about 1400 gallons and had water in it for about 3 weeks.  I put a Zoanthid colony and a Pom Pom Xenia colony in it a few days after I got water in it.
<? Why would you do this? Neither appreciates a new setting; both are very allelopathogenic>
  The corals immediately showed signs of stress and since then the Zoas have bleached out and the Xenia has remained shriveled never opened up. 
Neither have died, but they look like they wish they were dead.
I used Seachem's Salinity salt.  Alkalinity is 3.0 meq/l and PO4 is .04 according to my Red Sea test kits.  My S.G. has ranged from 1.023-1.026 (due to some plumbing errors and programming learning curve).  My pH has been very stable at 8.15 and temperature ranging from 73-74.  I'm using Neptune's Apex controller and probes which have been calibrated to manufacturer specs.  My ORP in my main system is reading steady around 170.
<Strange... due to the exudations of just these two (probably small) colonies? Something else here>
  ORP in my RO/DI water is reading at 300, in my SW mixing tank it's reading 200, and in my SW reservoir it's reading at 190.  I've spent hours reading about ORP, but frankly it's just a lot to grapple with and doesn't seem to jive with my readings.
<Agreed... have you certified the probe is reading accurately? I would check it against one or two standards>
 I'm using an MRC skimmer, which is getting a surprising amount of skim for the 2 tiny corals. 
<? Again; what is going on here? Some other source of pollution. I would place some pads of PolyFilter in the filter flow path; check for color>
The system is a frag unit,
<What is it constructed of? Has it had a good deal of solvent (like PVC) used in it recently?>
so it has a lot of surface area (~200 ft/sq) and is in a pet store with puppies so it gets a LOT of dust (like, store has to be professionally dusted once a week) so I'm assuming that's where most of the protein is coming from.  I'm also running water through a reactor with filter floss and a big bag of Seachem's Purigen.
Mysteries that you've hopefully already solved for me: A) Why do my corals hate their lives? B) How do I interpret my ORP readings?
Thanks,
Scott
<Does this system have an ozonizer installed on it, a calcium reactor... CO2 driven? Bob Fenner>
RE: Low ORP    2/23/14
Chose the Zoa and Pom Pom simply because that's what I had healthy frags of, was avoiding a livestock order until I had healthy water.  Is it possible my guinea pigs just hate the "new setting"?
<Oh yes; for sure>
 I assumed with no fish, no bioload to speak of, and a massive water volume to dilute un-desirables... it would be a near ideal setting. 
As to your other questions:  Yes these two corals are quite small. 
Re-Miscellaneous pollution.  Yes, there was recently quite a bit of solvent; the entire system has been plumbed within the last 60 days using the expected arsenal of PVC cement, silicone sealants, etc.  The display tanks themselves are glass (our custom design, crafted by DAS), but we re-purposed (thoroughly cleaned) barrels and totes for the fuge, sump, bio filter that might have had residue from "accuslurry" or whatever they were transporting.  I also used quite a bit of Vaseline
<Mmm, don't use this... petroleum product. Look instead to silicone lubes... as made for O-rings on pools, cameras>
 to get the plumbing through all the Uniseals (which I have used safely in fresh, but don't know if saltwater reacts chemically).  I expected that the Purigen (similar to PolyFilter I believe?)
<In some ways>
 would remove miscellaneous chemicals, perhaps it is and hasn't had enough time.  Will add PolyFilter this week.  Seems like chemicals are likely and I should probably be pretty aggressive about eliminating these unmeasurable, untestable, unknowns?
<Mmm; no; not really. There is a very wide/range of chemical properties at work here... There are no "do all" chemical removing media>
  Re-ORP accuracy: Neptune claims that their probe is pre-calibrated and will never require calibration for the life of the probe.
<What? No... do you/they have a reference that actually states this?
Unbelievable; or... at least to my awareness; impossible>
 Do you recommend supplementing an additional probe or trying to calibrate the one that I have?
<The latter for sure... Likely weekly if employed full/real time>
 Lastly, there is no ozonizer currently, add one this week?
<Maybe... depends on what the folks are keeping, hope to achieve... skimmer first, then O3, then dryer, then Ca reactor...>
 Calcium reactor exists but has no media or C02 hooked up yet. 
Thanks again,
Scott
<Welcome! BobF>
RE: Low ORP    2/23/14
Can you explain (or refer me to literature, if too complex or lengthy) that explains biologically/chemically what transitions a tank from a "new setting" to "old setting"?
<Wish I could... don't know that there is such>
 I'm familiar with basics of the nitrogen cycle, but with 1400 gallons and two tiny corals ammonia couldn't be present in any significant quantity could it?
<Not much; no>
  Temp, pH, alkalinity and SG are acceptable.  What are the other key variables?
<NO3 and HPO4 are necessary... as is some ferrous; other micro-nutrients>
Regarding calibrating the ORP probe:
http://www.neptunesystems.com/wp-content/uploads/2012/09/AquaController3Pro.
3_2_web.pdf (page 26, first two lines).  You calling BS on these guys?
<... This: "Calibration of the AquaController III Pro is quite simple, and should be checked at regular maintenance intervals to insure accurate operation.".... is what is posted for the Conductivity probe... not temperature... I don't know what they mean by "regular maintenance intervals"... but again, I'd be checking weekly>
Regarding stocking plan and equipment, it's an 8 unit 5'x5'x8" centrally filtered coral/frag display.  No fish.  It will contain the full spectrum of corals you would expect to see in a retail environment (insert allelopathy snipe here ;)).  It's got a huge skimmer and calcium reactor already.  Could def add ozone, we talked about it extensively but was left out due to indecision.  Have never used (nor heard of, honestly) a dryer,
<... see WWM re>
 but brief research suggests it's a practical addition.  With sustainability in mind it only makes sense to spare no expense.  Keeping the system/livestock as healthy as possible is = to compassion, fun and long term profit.  I have been a 'conscientious marine aquarist' for over a decade now, and trust your advice.
Scott
<Ahh; cheers, B>
RE: Low ORP
Edit/fix on my last message - I said page 26, was actually page 27. 
Additionally, here is a copy/paste of the section I was referencing,
"ORP Calibration   
It is not necessary to calibrate the ORP probe of the AquaController III Pro. It has been properly calibrated at the factory to maintain accurate ORP readings for the lifetime of the controller. However, it is possible to calibrate the probe if so desired"
<Interesting... and new/s to me>
They have a 'special' probe for ORP, the conductivity probe is used to measure salinity.  Will still calibrate as you advise, but wanted to mention this lest I soil the chronicles of WWM with misleading information.
<Ah good>
Thanks,
Scott
<Thank you, Bob Fenner>