Pics of the offending stain attached. Problem is it's right in the middle of the deep end around the main drain.
I started with a chlorine push and the broom - tried to "scrub" the bottom with it, but couldn't really get it going. I let it sit overnight and thought maybe I saw some improvement, but I can't be sure.
Bought vitamin C and put it in a sock. It wouldn't sink so I tied it to the same broom and pushed it onto the bottom. Doesn't appear to be having any effect.
I'd like to try scrubbing with a chlorine puck, but I can't come up with a good way to get it down there (and have enough force behind it to actually "scrub" the bottom). Any tips on next steps here?
FC 10 (coming off shock)