Tank and sump salinity different ?

[rusty hannon]

Morning all, we, my wife and I, set her 55gal corner tank up 6 mo. ago w a 26gal bashsea sump. We cycled it, added turbo 900 for an extra kick and on we went. Everything is perfect but one thing , salinity. Its not necessarily a problem as a curious ordeal. Since day 1 the salinity in her tank has been established at 1.023. The strange thing is her sump is always .001 point higher than her tank. The water is mixed and aerated in another bucket and left w a pump for several hours before being added. We've tried adding the water to sump, or tank alternating to see if we can get them in sync but no luck. Any ideas or clues as to why or anyone else experience this?

 

[Dbichler]

Most likely the temperature difference from dt to sump