ATI ICP discrepancy with salinity

[Ziggy17]

So I got my ICP test back and it said my salinity was 32 ppm. But I keep my salinity at 35 ish give or take .2 swings with temp swings. But I checked my apex for that morning and it read 34.8, and they day before I did a water change and put 35 back in according to my refractometer. And I always double check my ATC refrac with my old school hydrometer, to make sure the reading are the same. I also zero the refrac with tap on WC day.

There’s always a chance that my apex, refrac and hydrometer are all giving me the wrong reading, but unlikely. Also, the corals are great and the inverts are all doing well too.

Has anyone else had the same issue with ATI and salinity? Is there something in the shipping time/process that could decrease the salinity a full 3ppm????

 

[exnisstech]

I don't remember what my salinity was when I did an ATI icp a couple of years ago. I sent in two seperate test from two tanks including rodi samples pulled from the same container at the same time. The rodi result were so different from each other that I had zero confidence in the test and binned the results. I trust my refractometer and hydrometer more than any icp test. JME

 

[KStatefan]

No experience with the ATI test but are they measuring salinity or calculating it from the ICP results?

 

[H.E. Pennypacker]

I would also trust your hydrometer over the ICP. I'm going to be sending an ATI ICP out next week so will keep an eye out for this.