I use both SM-90 and Hygrozyme in my Hempys and DWC's. 2.5 mL per gallon of SM-90, and about 5mL per gallon of Hygrozyme. SM-90 is good as a foliar spray for mites too :)
As it was said SM-90 is supposed to work with hygrozyme, cannazym etc.
I don't use it because i like to keep my good bacteria alive, as I inoculate my media with Great White.