Thanks for posting. 25oz seems like an awful lot of bleach; though I can see where that would definitely "shock" the system.
My method is more like your last line saying to use half of that bleach. I use a quarter cup of household bleach for every fifteen gallons of water that my fresh water tank holds. That would be 1.7 cups for a 100gl tank or about 13.5oz.
I let mine sit for 24 hours, but 12 would probably be sufficient.
DW, 3 Kids and our Goldens
2012 Shamrock 233S
2008 Toyota Sequoia 5.7L 4WD