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.

A complete flush requires some nutrient to pull the salts from your plant and media

PhatNuggz said:

A complete flush requires some nutrient to pull the salts from your plant and media

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And what are you using?

No Flushing here, just tapered nutrient strength till the last feed is plain water.

Medigrow said:

And what are you using?

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the nutrient doesn't matter. it's science

MidwestToker said:

No Flushing here, just tapered nutrient strength till the last feed is plain water.

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I'm trying to debate about using a flushing product, like florakleen or advance nutrients' vs water only

Sorry, as I've been strictly a coir grower the last 10 years and as is such changes in nutrient levels show up with-in a day or 2. So I never found the need for a flushing agent or the added cost.
You can still get a good fade while still supplying nutrition to the plants.