Yes, I’m given to understand that the Rabbis draw the line at anything too small to see with the unaided eye.
NYC tap water needs to be filtered to remove just barely visible copeopods to be considered Kosher.
Again, whose “unaided eye”?
I’ve been able to eye-read micron-size etched numbers from optical elements, for years.
These arbitrary qualifications for things to be deemed equally arbitrarily “clean” or “unclean” always crack me up. The jokes are all halal!