does anyone use Neptune PM1 or PM2

[+Mitch]

Just curious if anyone uses either of these modules to measure ORP and/or salinity? If so, what are your thoughts?

[Juiceman]

I measure ORP, it's not really needed, but you can see if something died or the skimmer is not pulling or etc, because your ORP will go down. But I really don't pay attention to the actual level, just it's raising and falling. I would think salinity is not needed if you check it regularly with a hydrometer or refractometer. A recent pic from Mr. Saltwater tank showed his salinity probe sitting at 35 ppm, and him saying its the most boring graph on his tank.

[victoly]

Professionally speaking, ORP probes need more frequent calibration than pH probes to give you good data, and unless you're running ozone, it isn't really a great indicator of water quality. Like the juice said, just watching rising and falling. As for salinity, it's another parameter that's just going to give you a failsafe (i.e., OH CRAP I DUMPED ALL MY ATO WATER!). IMO, neither are worth the expense and calibration duties.

[Richard L]

Same here. I have both and tend to ignore them partially because they have not been calibrated in a long time and partially because they rarely change. Good point Victoly on using salinity as a failsafe for a runaway ATO. I need to add that into my programming.

[George Monnat Jr]

I use the PM2 for salinity, because my ATO adding limewater causes fluctuations. My PINPOINT Salinity Monitor drifted badly out of cal leading to very high salinity levels as I added salt. The two hydrometers I have are also unreliable and were poor choices for redundant/backup reading. So I got the PM2 to monitor DT temp and salinity with the original temperature probe and PINPOINT monitoring my sump as a redundant/backup monitor or sanity check. Here's my DT temperature and salinity (both from PM2) for the last week:

Not exactly flat, but I want it to be. Some fluctuation is from temperature, some from ATO and a lot from a recent 25% water change and changing from IO RC to aquavitro salinity. As you can see, aquavitro salinity is more potent, so I overshot a bit. Now I'm pulling a little water out of the sump each day to allow the ATO to slowly drop the salinity. Adding more kalkwasser is a bonus. Once I get the conductivity to 53.0 mS/cm when the sump is full (ATO off due to float switches), then it should remain constant. But I'll probably keep tweaking it for pH/dKH/Ca with kalkwasser addition. My pH/dKH/Ca has been rock steady.