Why is it that most posts I see people posting 60-80 cya levels and only 2-3ppm FC levels? When I look at Ben's best guess it should be 5-10.

I did the same thing all last year and didn't have any problem, but this one has always confused me. I know it's called best guess, but why don't I see more people with levels that match up? (Maybe I just notice them more....)

Do the SWG allow lower FC levels or am I missing something?

(33k gal, vinyl, Aquarite)