Has anyone seen these before?

I have theses weird tunnel looking things does anyone know what they are and what they are from? And then does anyone know why my sand is discolored deeper down?Attachment 174994Attachment 174986

Also does anyone know what these bugs are I know I have asked this before but no one seemed to know.Attachment 175002 it is the little red bug in the corner(sort of in the corner of this pic)

Attached Thumbnails