Yes. that is right.... you do have to use the tub to make the chemicals work. we use a mushroom type floater with pucks.... I find that set at level 7 I do not add bromine. the biggest thing I find is a product called "perfect balance" and "refresh" - if these two products are used religiously after the tub has been used, I have no other issues.... I should say I'm on a 147 ft drilled well.