They call it a root zone conditioner. I don't know what it actually is, but it's not for the plants. It's for the water/ Rez. I've never dealt with stuff growing in my Rez, never had slimy roots, never funky smelling Rez (not sure why the iPad keeps capitalizing Rez). a difference I can see with my eyes is the bubbles. The zone powers the surface tension of the water and so bubbles have an easier time getting made. Not really a scientist so my description sucks. With no zone my waterfall makes bigger bubbles and not too many of the,. Win zone the bubbles turn tiny. Get deeper in the Rez, and I think it helps get more oxygen dissolved in the water. That's just my idea though.
Only 1ml per gallon too. Lasts forever.