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DWC: top-up nutes, or full water change?

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    HYDRO DWC: top-up nutes, or full water change?

    What is best practice for nutes in a DWC grow (5gal pails)? Do people just add fresh nutes to the existing water, or do a full water and nute change?

    Should this be be done weekly?

    Using my EC meter, my tap water measures at ~120 ppm before nutes. After adding nutes the ppm is ~350. Near the end of the week, the ppm has only dropped to ~280 ppm. I don’t know if I should “top-up” or do a full refresh.

    Over 30 yrs of back pain management without ever having a pharmacist give me a bottle of pills. Thank you Mother Nature and all the hippies from the ‘60s that became weed-masters.

    Howdy YYCannabis, I grow in six gallon totes (GH nutrients and supplements) and I start the feed cycle off with the water (pH'ed to 6.0) and the nutrients required (for age and photo period of the plants). At the mid week I add (top off) just plain pH'ed water. I check the pH of the reservoir and adjust the pH of the top off water accordingly. If the reservoir is over 6.5 then I pH the fill water to 5.5 or just slightly higher, if the pH is below 5.5, then I adjust the fill water to around 6.0 to 6.5. Most of the time the pH is around 6.0 to 6.5 and I just make the fill water at 6.0. The pH needs to vary within the range of 5.5 to 6.5 for proper nutrient uptake by the plants, so it is best to let the pH 'swing' within those numbers.
    Smoke weed,.....grow peace!


      I would highly recommend that you do a, complete water change weekly and throughout the week just top off with plain ph'd water. As dw2 said ph is important so I would also recommend checking your ph at least daily and adjust accordingly. I sometimes check mine 3-4 times a day.


        Thanks folks.

        I do watch my pH daily and keep the range between 5.6 and 6.5.

        But for the nutes, I should just add more in accordance to the decline in ppm at mid-week? That seems manageable. 👍

        Over 30 yrs of back pain management without ever having a pharmacist give me a bottle of pills. Thank you Mother Nature and all the hippies from the ‘60s that became weed-masters.


        • Formernuke
          Formernuke commented
          Editing a comment
          I didn't know about a 24 flush every month what's that do for them?

        • SirSmksAlot
          SirSmksAlot commented
          Editing a comment
          I would only add nutes when you do a water change. Mid week top off should be plain water

        • YYCannabis
          YYCannabis commented
          Editing a comment
          I misunderstood their comments. I think I got it now 😉
          Thanks for the clarification.

        YYCannabis If you're running a larger system, add back rez management is more practical. If you research Lucas Formula, you'll find some growers who run strict add back systems and their management techniques.

        I'll often skip a couple of full nutrient changes during flower. With four plants in my 90 liter system, they'll drink 10 -15% of the rez every day and consume roughly that same amount of nutrients. Instead of topping with straight RO water, I'll add 10% of my Bloom and CalMag to the topping water to maintain the solution concentration at a more constant level. I don't put all the additives in, just the major proportions.This helps mitigate big swings in the pH for me as the Maxi nutrients provide buffering.
        Space 1: 3ft x 3ft T-Tek tent
        400W HPS Mag Ballast
        GH Floro - DWC
        Current grow - Humboldt Fem Green Crck from seed
        - TGA GSC x Space Dude clones

        Space 2: 6ft x 6ft x 8ft room
        IponicZone 400/600/1000W dimmable HPS E-Ballast
        Supplemented with California Lightworks Solar System 275 with spectrum control
        GH Maxi Series-DWC
        Current grow - Humboldt Fem Blue Dream from seed
        - Humboldt Fem Blue Dream Clones
        - TGA GSC x Space Dude from reg seed in dirt, G.O. Box nutes


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