HW Reefer Salt and ORP

dragon99 · Mar 2, 2017

Just an observation I suppose. I've found a post from Randy about this and his answer was that the salt mix probably contains redox active metals.

Salt mixed to 35ppt on Milwaukee (Apex reads ~35-35.5)

First water change with new salt was 12g , but only ~30% of salt was HW Reefer, rest was IO. The second little drop was a 5g WC when I replaced my carbon/GFO.

Next water change, 15gal (20% of total volume) with all HW Reefer salt caused a pretty large drop in ORP with a slow recovery.

dragon99 · Mar 2, 2017

Here's a previous water change with just IO as a reference. Initial drop from stirring up junk/vacuuming sand, but an increase in ORP after it settles:

Aaron Atkinson · Mar 2, 2017

I use the same salt and experience the same phenomena. No real issue so far as I can tell

saltyfilmfolks · Mar 3, 2017

Very cool...I believe, and correct me if im wrong, its the visual representation of why ORP isn't a good indicator of tank health. As changes are easily made by a multitude of very common and harmless actions or additions.. Its to broad an observation to troubleshoot a specific problem.

hart24601 · Mar 3, 2017

TMP did the same thing for me, dropped ORP drastically. Nothing to worry about.

jwshiver · Mar 6, 2017

Had the same results when I used to use HW. It would take until the next weekly water change for the ORP to come back up. Of the three salts I've used it is the only one to do that.

dragon99 · Mar 6, 2017

saltyfilmfolks said:
Very cool...I believe, and correct me if im wrong, its the visual representation of why ORP isn't a good indicator of tank health. As changes are easily made by a multitude of very common and harmless actions or additions.. Its to broad an observation to troubleshoot a specific problem.

Exactly. The only reason I have it is because Neptune includes it. I won't be replacing this probe when it goes bad unless something changes. Maybe if I was running ozone I would see value in ORP readings.

Aaron Atkinson · Mar 17, 2017

What I like about the ORP probe is it can be an indicator of Skimmer or Water Flow trouble. When the skimmer stops working, like when my pump froze due to calcium build up, I could see a fairly rapid drop in ORP. Makes sense to me because less oxygenation of the water was occurring. On the other hand, when my return pump did the same thing, I saw a fairly rapid rise in ORP because the skimmer was oxygenating just the sump water volume.

Of course, I've revamped my pump cleaning maintenance schedule. FWIW, maybe you can find some value in the ORP probe other than just when things die it drops quickly.