Hi there! I’m growing some Gorilla Glue autoflower in a 2x4x6 tent, one plant right now. Growing in FF OF on the bottom, HF on top in a 5-gallon fabric pot. We’re in week 5. Using GenHydro Flora series nutes, very lightly now, diluted in rainwater. I add nutes to rainwater and pH to 7.0 (high, I would say), TDS about 250. Here’s the problem: runoff is 3.4, 520. I immediately add rainwater pH’d to 9, now getting runoff about 5. WTF?? Rainwater alone has TDS about 20, so pH swings fast. Suggestions?
When is the last time you have calibrated your instruments? Also welcome back and always post a few pictures to help us with a visual.
I would recommend doing a slurry test of your soil once or if your tester is accurate.
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Also i would suggest cutting your rainwater with some tap water. Tds of 20 will be very hard to adjust ph accurately. 100 or higher is what i go for if i add ph up/down
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I have found with FF soils they are not always canna friendly out the bag. I had a bag of OF last year with a pH of 5.2 doing a slurry test. I was seeing some really low pH readings at run off and that is when I realized, gonna start testing every bag when I open it. It has been the only bag I had issues with. Also when opened, gnats flew out.
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I use happy frog , and plan on mixing in some ocean forest. But i used advanced nutrients, requires no ph adjustments. I also use rain water. Once i had all my nutes and stuff ph is usually round 5.9 to 6.5 . Run off always comes out at 6.9 dont know how. But i was always told to ph after adding nutrients, but im also a beginner to so … not sure if I’m any help .?
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My situation is not the same as yours but for what it’s worth, I’ve had pH issues using FFOF before too. I sometimes get some fluctuating numbers from the run-off, usually high. Same with slurry tests from different locations. I used to chase it all the time, trying force it down with different suggested additives but mostly by pHing low going in. That never worked out well, caused more problems. Noticed the run-off pH would spike at feeding, more with one line of nutrients that another. Finally bought a soil pH tester and readings were not as crazy as the run-off was indicating. I stopped chasing it and let it find it’s own happy medium, pun intended. 
Sometime my run-off spike upwards to 8.0 ish, makes me nervous but the ladies seem much healthier since.
Had some of these from FF too …On my first grow Aaaargh!! 
That sounds right! I think that makes sense: one Drop of pH up or down affects it a lot. Baby’s looking good though!
Baby is looking good, nice work. Idk if others agree but maybe raise your light a few inches. She is definitely stacked, might help free it up a bit.
I did recal on my Apera PH20 today, very small change.
Thanks for all your support! Getting some strength in the water to affect the soil is right on, I think. Carry on, right?
Numbers can be scary sometimes. But the most important thing is what your plant is telling you. If they look happy, they probably are happy. If they look sick, then they didn’t like something, you gotta figure out what needs to be done. Great looking plant, i wouldn’t be surprised if it started stretching for flower in the next week or two
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