I am another one dealing with this crapper.
I had some brown spots on my walls even. Is it sometimes even on the walls? Aaarrrgg!!
I thought I was rid of it, but it is back now that the chlorine level has returned to normal. Will the stuff ever die? My filter cartridge is yellowish brown every night when I hose it out.
I don't wanna shock any more!! I held it there for days. The chlorine held overnight and drifted down to normal...that is when the sucker came back.
I want to swim, not shock.