I've heard good things (mostly) about HydroGuard. I'm partial to the idea of using a product to hold off anything from getting settled in to your soup that you don't want, rather than having good low 64-68* temps ensures a healthy Oxygen RICH media for your roots to soak in and looooove. It's nice and cool 4'+ below the earth, trust me. You starve your roots of much needed o2 by having anything above 70*ish.