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Why does my PH keep dropping

Discussion in 'Indoor Growing' started by b2krawler, Mar 27, 2010.


    b2krawler Member

    im almost at the end of my grow,
    aeroponics, purple kush, 2000watts HPS, GH3 part nutes (aggressive bloom), 1200-1500ppm, I flush every two weeks at rez change

    I bring the PH to 5.6 everyday and in the morning its in the 4.0 range, everyday.

    is it because my plants are on their last week b4 flush?

    is my ppm to high, it didnt do this a week or two ago, i even almost got to 2000ppm, w/o problems, (a little burn, so i backed it off)

    is this normal thing when the plants are ready? the PPM stays pretty consistent and its still using a lot of h2o?

    this is the 1st grow i went above 1200ppm, buddy has similar setup with same plants and often hits 2000ppm, my temps are good (rez and air)

    i hardly ever need PH up, now im using it daily

    wiseguy316 Well-Known Member

    take a look at your roots, they may explain everything, my ph only drops like that when i have a root problem.

    SickSadLittleWorld Well-Known Member

    I had similar problems and my ppm ended up being way too high. Once I backed off, the pH didn't fluctuate anymore. Sounds like you've got your ppm dialed in for the most part but just throwing it out there.

    b2krawler Member

    roots look happy

    wondering if it had something to do with them being ready, im at 8 weeks, start flushing tomarrow.

    I did have same problem a few grows ago, ppm was too high, but it was only week 4 or 5, this time it waited until the end for the PH to go nuts.

    should you lower ppm in the last week or two b4 flush? i would think thats when it should be at its highest?

    im actually going to 9 weeks for the 1st time, just to see what happens

    SPODE Member

    I'm also in the same situation. I found this same discussion on another site.

    The most interesting part I found was by BigAl. He wrote:

    "Your plants are probably taking more water than nutrients. As you would already know, adding nutrients to water lowers the ph.
    Is it possible that your misters are contributing to the loss of water through evaporation?
    This is where checking the ppm regularly comes into play. If your plants are taking water and leaving nutrients in the reservoir then you are feeding them too much."

    I was under the impression that if a plant isn't burning then load it up on nutes. But his response seems to suggest that you can overfeed a plant without burning it. Is this true? But then again I'm not overfeeding the plant if it isn't using the nutes, I'm just being wasteful and putting the plant through a lot more stress and making it susceptible to other stress related problem by having large fluctuations in PH. Is this accurate?

    Currently I have plants that are under a 1000w HPS light, 28 inches tall (on average) and in their fourth week of flowering at 1575 PPM. Although the plants are not suffering from nute burn could I be overfeeding them and this is why they are taking in more water than nutes thus concentrating the PPM and in turn lowering my PH.

    Is this true? More isn't better even if your plants are not burning...?

    SickSadLittleWorld Well-Known Member

    Makes sense to me and that is why I suggested it may be PPM related. Less is more with nutes and I suspect you are grossly overfeeding.

    1500ppm sounds really high regardless of strain. I'm at 800ppm going into week 6 of flower on my trainwreck, for example. Even though the plants aren't burning, I'll bet they are showing other signs of overfeeding and would benefit from lower ppms.

    killforkush420 Member

    my buddy having the same prob and have been looking for some input: using advanced nutes, rockwool, 6thweek flower,500L res, just changed res five days ago and ppm was 1200 and ph 5.7-5.8, after two-three days the ppm went up to 1450 and ph went down to 5.3. only lost 50L in res ph would prob go down further but check it everyday,happened at end end of last week and added R/O'd water so ppm was 1300 and added ph up back to 5.7-5.8.(was it right thing to do?)i adjusted the the same way the past two days. should i bring ppm back down to 1200 since ph didnt jump as much or is there something else i should be looking at? any info will help:weed:

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