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Hydroponic PPM question.

Discussion in 'Hydroponics / Aeroponics' started by mmaaddmmaann, Jul 11, 2008.


    mmaaddmmaann Active Member

    Hey guys. Quick question about my hydroponic setup. I check my PH and my ppm, both using digital wands. I was wondering if anyone knows why my PPM reading would go up over time. For example, my last nutrient change was 3 days ago. My plants are about 7 inches tall, and healthy. I have my nutrients at 300 ppm at feeding time. 3 days later, my PPM reading is 460. This has consistently happened to me in all my hydro grows. I am using Clay pellets as my medium and general hydroponics, grow, micro, and bloom formulas. It's all under a 600 watt MH HID bulb in a 4 by 6 by 8 grow room. The light is about 3 feet from the plant and is ventilated with a fan. Thanks for the help guys.

    KAOSOWNER Well-Known Member

    well when your ppm's go up it means your plants are drinking more than they are eating. (using more water than nutes)

    mmaaddmmaann Active Member

    thanks KAOSOWNER. SO I wonder what the best remedy is for this, adjust my ph so allow the plants to absorb more nutrients? I typically have it around 5.8 - 6.1. Other than injecting Carbon dioxide into the atmosphere, is there a way to have the plants eat more??

    gohydro Well-Known Member

    No...you want your PH to stay around 5.6. Forget what you read about what others run in terms of PPM. Don't try to compete. All systems are different based on lighting, hydro type (NFT, Aero, Drip, etc.) temps and a myriad of other things. I see people talking about 1500-2000PPM in their systems but those are THEIR systems and THEIR environments. I could probably get away with 900PPM in my drip systems but if I go over 650-700PPM in my aero systems I'd kill everything. I like to see my nute strength drop 50 or so PPM over a 3 day period. That tells me that I am just about where I need to be. Your PH will always change (less if you use R.O water) but you should still check it at least twice a day and adjust as necessary. Too far out of whack and you'll cause nutrient lockout.

    New Papaya/Kush Journal with pics

    mmaaddmmaann Active Member

    So am I to understand from your post (gohydro), that my plants will drink and eat around the same if my nutrient strength is adjusted precisely? For example, if im currently at 300 ppm in my system, and im gaining about 40 ppm a day in nutrient strength, i could dilute my resivoir to lets say 200 ppm. After doing this, i might see that with that strenth (for the current stage of my plants) will give me a better ratio of drinking water to eating nutrients. I would obviously need to do some testing to see how my resivoir and plants react to get the right balance. But is that the general idea? Put only enough nutrients so that my plant drinks slightly more than it eats?

    gohydro Well-Known Member

    EXACTLY! You want your nute strength to stay somewhat constant. Forget what others run. If it's going up then as the last poster said "they're drinking more than they're eating". If it's going down (PPM) then they're eating more than drinking and your next mix could probably be a little stronger. If it's going up I'm assuming you can see the telltale signs......maybe tiny burnt leaf tips. Just remember the tip about PH also. Too much fluctuation isn't good there either.

    Xan2 Well-Known Member

    Many factors will raise the ppm. Dust, algae, dirty hands in the res... Anything that is mineral will raise the ppm.

    Also, water evaporate but not salts and minerals. Tap water also play a factor.

    smokie927 Active Member

    Nitrogen is best absorbed at a PH of 5.8 in any DWC that i've encountered, you dont ever want to go below 5.5 or above 6.3 and 5.6 is a little too close. Like gohydro said every system is different,you need to find what best suits all the conditions your running,not what someone else is. I'd go into the ppm thing but people already got that covered,nice thread. Stay up Oregon,the cHronic State. Dont leagalize Marijuana. Smoke joints.

    oJUICEBOXo Active Member

    Yeah I agree with smokie....here is a PH chart. I let mine drop to 5.8 then raise to 6.2.
    View attachment 1146096 [​IMG]
    rob the snob

    rob the snob Member

    so hey guys i have a question ..... i have a ecogrower with 17 gallon reserv. and i just got my tds meter and it said that the water was 157 ppm how do i fix this .... i fed the plants last sunday general hydro series today is tuesday and i just did the test.. please help!!!

    Grow4216 Member

    Hello everyone I am a first time grower with a Hydroponicssystem my seeds have been in the rockwol now for one week. I plan on changingthe water and nutrients out tomorrow. I am watering the seeds four times a dayand for fifteen minuets each time. I am keeping my PH at 5.5-6.3 so far am Idoing everything right? When do I need to turn the light on? Is it when theseeds grows out of the rockwol? Thanks for any help.
    match box

    match box Well-Known Member

    I have a ebb and gro system 2 gal buckets. When I change res it doesn't get the water that is in the bottom of the pots or in the water lines. I adjust ph and check ppm it's all good but as soon as the system runs the water in the buckets and lines will change those readings. As my plants grow more roots it also is harder for the water to fill right so I had to go to 30 min per watering from 15. I also had to put 1" spacer under the pots so I didn't have a lot of water left in the bottom of pots to rot roots. I don't know if any one else has had to play with there system. I hope this will help if ya are running the same kind of system. MB

    DeeTee Well-Known Member

    I get the feeling you stand the chance of drowning your plant soaking for 15 mins. same goes with the seed, I just let the rockwool soak up as much as possible and let it go, once the cube is soaked that's all it needs, your roots shouldn't sit in water too long. 5.5 ph in my opinion is too low, it should be 5.8. you can turn on the light any time I keep it on all the time in case it sprouts and I'm not there to see it to turn it on, good luck with your grow.

    DeeTee Well-Known Member

    I've also learned that certain strains tend to like diff ppm's than others.

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