I looked at the MSDS and labels for both baquacil and baquaspa shock. They both contain the same thing, Hydorgen Peroxide. The only difference is the concentration. To cut down on costs has anybody ever used baquacil shock in a spa? Baquaspa shock is 7.5% concentration and Baquacil shock is 27%. It stands to reason I can use baquacil and only use 2 oz for approximatly the same dose as baquaspa at 7 oz? Does anybody have any other informaion or know of a reason I can't subtitute baquacil for baquaspa?