Prodigy

If you "really" want to get rid of the bio film use "Ahh-Some". When you use Ahh-Some, make sure you add enough chlorine to maintain a good sanitizer level (between 5 to 10 ppm). It's also not wise to breath any vapor during the flushing procedure because it's pretty obvious your tub is seriously contaminated with bio-film. It's simply incomprehensible that anyone would direct you to use five gallons of bleach in a 410 gallon hot tub!