Display to Sump salinity differences

[Martingale]

I have a 40 breeder tank, with basically a 40 breeder sump that I am setting up. Around 24 hours ago I had dump a bag of salt into the display and mixed it with a drill to 1.027.

However, 24 hours later, I then tested my salinity in the display and it was still 1.027. All good, right?

Well I planned to move my livestock from another tank into the sump while I finish the display, so I decide to test the sump salinity and my readings made no sense:

Return section salinity: 1.010
Skimmer section: 1.012
Refugium section: 1.013:

But the filter stock section read at 1.027 also. The return pump is ~350gph, but theres a few feet of head height of course.

Is this normal to happen? I would've expected the water to mix after 24 hours.

I had actually went ahead and stirred each section of the sump with a drill and it changed all of my readings again:

Display: 1.025
Return: 1.018
Skimmer: 1.020
Refugium: 1.022
Filter sock section: 1.025

This is all done with a Milwaukee refractometer, wiping off after each test. They're pretty consistent and I've done it multiple times scratching my head. There was no visible salt anywhere in the tank or the sump that hadn't gone into solution, and I was testing by pulling water from the first inch or so of water in each section.

I assume it means the flow in the sump is just really low, but will this cause issues with using an ATO or anything? It always reads like a slow flow through your sump is ideal for the skimmer/refugium.

 

[jaxredsoxfan]

I would check it again in the sump in a day or two and see if it stayed stable at the stirred rate or did it drop. I think regardless of the flow if the salt is mixed it should permeate everywhere. I would expect less salinity in the chamber an ATO feeds but it should stabilize throughout the rest of the system.