I’m not sure where 50% effectiveness comes from?I’d be out a substantial amount of money as well as reputation if we were only getting it right half the time. I’ve done well over 150 applications (after doing proper turbidity testing) and have had 2 not clear up, one was well pumping 0 hardness water back in the other one was weird runoff. Have had to reapply maybe 5 times mainly after tremendous rainfall. Alum is much more effective than gypsum in binding up excess nutrients to reduce a bloom but that is only temporary patch as they usually go back green within a couple of months.