Display NODATA values

[RuthBeusing]

Hi all, I am new to raster processing in ArcGIS Pro and for some days now I try to visualise magnetometry data (Golden Software Surfer7 files) correctly with the software. Everything works quite fine except of the display of the Nodata values: zoomed in from 1:1.128 everthing looks as it should (img1) ...

but when I zoom out the Nodata values are displayed as white pixels (img2), though the Nodata is defined as transparent.

I tried out several things to solve the problem and searched the arcgis pro help and the internet for similar problems/solutions, but couldn't find anything helpful. Maybe someone here has an idea?