Hydrogaurd is nothing but bacillus amyloliquefaciens its pretty expensive and im using southern ag fungicide now at 1 ml per 20 gal. The southern ag fungicide does have some organics so you will see maybe a bit of foam like enzymes. The southern ag fungicide is dirt cheap and much more concentrated
The bacteria will kill pythium and protect roots from many different infections Not just pythium and has been used in big ag for decades for this reason.
The enzymes will help eat up any root shedding or decaying organics that pathogens feed on.
So the combo of the 2 while not absolutely necessary works wonders. But you can run either or in which case I would probably go with the bacteria.