I had the exact same issue. My clear filter was turning pink but there wasn't any real crud in it. When I unhooked the line from my tank I barely got a trickle. Finally got it drained and found a couple pounds of red sand in it.

I ended up getting a new Spectra tank from RockAuto for about $150 shipped.
The quotes I got for cleaning and relining the old one were about the same ($125-200) but I've heard a lot of stories about the epoxy lining getting gummy after several years of use so I decided not to chance it ... and for the price, it was a no brainer.