Hydrogaurd or SM-90?

I'll be starting my first DWC. I'm trying to stay ahead of root rot by preventing it before it happens. I've narrowed it down to Botanicare Hydrogaurd (formerly Aqua shield I believe) or Nutrilife SM-90.

Naturally conditions will be clean as they can be and temps will be well within a tolerable range, but I'd feel better adding something to the reservoir. Anyone have good results with any of these products?

I've had great results with hydrogaurd and h2o2. Not at the same time of course because the h2o2 will kill the bennies in hydrogaurd. I've never used sm-90 so I can't comment on that.

Hydroguard is great imo. I grow with my water always in the mid 70F's and don't have issues due to what I believe is the Hydroguard working its magic.

I think sm-90 is good as a bug repellant to spray the foliage but every time I ever put it in my res it made everything worse.

Everything worse? Don't like the sound of that. Hydrogaurd it is!