Spring tails originate outside your pool -- you have to deal with them there, before they enter the pool. Here's a fairly authoritative guide: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74136.html

And, a thread from last year: http://www.poolforum.com/pf2/showthread.php?14426

Other then physical methods (grinding, polishing), I've never seen anything remove the stains from leaving a chlorine tab on a concrete or fiberglass surface. They do seem to lighten somewhat over time.

By the way, if you'd be willing to give me high resolution pictures of EITHER problem, I'd be grateful.

{archived: "20419 - Dealing with spring-tails"}