I am typically a soil grower and while a lot of people don't, I do tend to have a "flush period" for my plants. I like to allow for a two week period where I am giving little to no nutrients. I begin this process two week before harvest. The first week of flush is
Botanicare Sweet @ 15mL per gallon of water given every other day or when the soil is feeling dry. The second week is plain water only and this is given sparingly, only enough to make sure the plants do no die prematurely. I actually like to allow my plants to dry out a bit before chopping. I use the Sweet for that first week of flush for two reasons, it is a magnesium sulfate product and the magnesium helps bind with other molecules and makes them either more available to the plants or begins to wash them out of the soil. The sulfur helps give the plants their aromas and flavors.
Now, I do use the Sweet all throughout the plants life, so it is not only in flush that I use it. And while plenty of people flush their plants with large amounts of water, I do not. I give as much water in my "flush period" as I do when giving regular waterings.
I know this is a soil based approach but I think using a magnesium sulfate product would work well in your RDWC system too. I personally would plan on 5 to 7 days with a magnesium sulfate product (Sweet, Flawless Finish, Mag Amped) and them 2 to 3 with straight water. Now I am saying this with no experience running RDWC, so hopefully someone with a bit more experience chimes in as well.
