Nutrients for hydro is a lot like nutrients for soil
basically, you mix them as directed and add them to your medium. In your case, you would add them directly into your water resevior. They will mix in and your plant will drink them up with the water. Be sure to keep an eye on your PPMs with hydro, as I hear its more important to maintain good levels with hydro as opposed to soil. Not sure why, but I have heard that soil acts as a sort of 'buffer' which helps the plant tolerate crazy ppms or something. Still unsure on that lol.
Once you get near harvest time and you decide to flush, you would basically drain your resevoir and put in clean water. I do believe there are 'flush nutrients' or mixes you can add too, but I have no experience with that. As far as I know, you can just feed water for the last week or two and be all set!
