pH, high ppms, and my steep learning curve

My first post on this forum was about a week ago and detailed some strange stress or damage to which I have all but attributed to light burn.

But in that thread, someone asked if I had checked my ppms. I had not. In fact, I had barely heard that term and only recently realized it could be rather important. I only had a cheap 3way meter and really didn’t understand the true depth of importance of pH in a grow.

So I got to reading and the more I’ve read the more confused I have become. That said, I got a tds meter as well as one for pH this afternoon. I just finished transplanting 10 Egmont Outdoor plants ( around 6 weeks now from seed) from 1 gal pots to 5 gals. I figured I would test the tap water as well as the runoff from the mix and see what I’m working with. Here are the results:

Soil mix:. FFOF + handful castings+ kelp meal 1/8cup

Tap water: 7.0-7.2 / 15ppm ( yes, that low. No RO or any other filtration happening in the line, apparently this city’s watershed is pristine)

Runoff: 6.7-6.8 / 2270ppm after first flush

So I am wondering what this tells me.
My gut says I need to pH down the water ( or is the proper term “up”?) to slightly more acidic so the soil ends up closer to 6.5.

But the ppms have me a little confused. Isn’t that 2270 number really high for veg? The mixture before this transplant ( from 4in pots into the 1 gal pots) was very much the same, minus the kelp and the plants are relatively healthy except the previous mentioned light burn on half of them. There are a couple runts in the group, so it could be assumed that the pH and tds are having their way with some of these plants, but I’m just too far in over my head to know right now.

Anyone out there care to help break down the situation for me in simpler terms? Or point me in the right direction?

My first post with pics and a deep ignorance of all this new info:
Wrinkled, folding leaves in half of my soil crop

The other post where I wrestle with my tds meter and my clean ass tap water:

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My first runoff of just straight ffof with nothing added was around 2800. Plants were put into a 5gal pot at 10 days old and never missed a beat. Some strains are more finicky then others I guess. I personally never had a problem and I never added any nutrients to my water until about week 8. What your going to do is every time you water you check your runoff like you did. And whenever your ppms or tds gets below 1000 is when I started adding nutrients. Wherever your plant is at in its life cycle, whether your still in veg at that point or in flower, you just pick up in your feeding schedule where your plants are. Hope that clears some things about the ppm in the ffof anyways. Again, thats just personal experience.


As @imSICKkid stated ocean forest has high runoff. I always presoak the soil a weak before transplant. Runoff is always around 2100-2200. Why this doesn’t burn the plants immediately, I still don’t understand. But as the weeks pass and you keep watering to runoff, no nutes, the Ppms will drop showing that the plant is feeding. I started feeding when I got to 700ppm. By that time I was at week 2 after 12/12 flip.


I was also in flower and picked up my schedule with the transitioning stage since they were still stretching hard. My ppm was actually at 800. But was told to stay around the low side of 1000


Thanks for the input. @imSICKkid, makes a lot of sense when its put like that. I’ve been trying to piece together info from all over the place and i think I was making it ultra complicated. Thanks for the breakdown.

One thing you said, @BobbyDigital, made me wonder… The second time I flushed water through the soil mix, the reading was a few hundred lower than the first. I just assumed that every time you water through to runoff, you would be leaching nutrients and the ppms would drop accordingly. Is that logical? If so, then how are we sure the plants are feeding based on the ppms, if we water to runoff each time? I suppose the numbers would just reflect a greater jump down in value? Thanks to you, too, for all the help here and in other posts!


That’s the importance of watering between feeding.

Say you start feedigg knowing your ppm is 500 in the soil. Then you feed with an input of 700. Your runoff should be near 1200. When you water to runoff after that you should be lower than 1200 if your plant is eating.


makes perfect sense now thanks!


another question about this ppm stuff:

in looking at the FF feeding schedule, there is a note stating “(700 scale)” in the PPM value row.

I found this explanation of the scales:

and apparently my meter uses the nacl 500 scale - so if I want to follow their schedule, am i supposed to be doing a conversion to sort out the difference?

lastly - the PPM values on that chart refer to the nute solution in water, not the runoff, correct?


You are entirely correct on all counts. There are some FF schedules that use the NaCl scale or you can find a conversion chart. That said I would only use FF as a loose reference for when to start and when to stop nutes. In veg using FFOF you need absolutely nothing and will likely develop issues. I don’t use vegging nutes in soil at all. Media like coco absolutely but OF is hot soil and has everything the plant needs.


Thanks my friend

I’ve definitely learned that OF is hot. The strange thing about it is that there is no indication of it on the bag, other than mention of castings and guano ( unless I missed the fine print). I definitely have some issues across my plants, but I haven’t yet attributed it to nute burn. I fed some grow big early on when it was too early, but luckily it was a pretty weak solution and I didn’t make the mistake again. Thanks to all you, I’ve decided to let them go and not even think about nutes until flowering… Even then I’ve seen a grow that it’s not even feeding and relying on the OF soil to carry it thru.

Thanks for chiming in



I am so sorry to hear, I know it is frustrating!

I to am a new grower and I just experienced the same thing. My PPMs was around 2500 on one of my plants.

If you would like to go back and read the last couple of weeks of my journal, you can see how I noticed the problem and what I did to fix it. Reading it like this might help understand rather than someone trying to tell you what to do.

Here is the link.

You can scroll back to the beginning the whole grow.

But if you want just the PPM issue where things got all out of whack, then i would just start reading here.
In which is about a week before I notice the problem.with my girls started.


cheers Bat.

that was a helpful read. things are becoming more and more clear now with every helpful post from the forum. nice looking plants too!

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Hey you bet!

I had not monitored the PPM until this point. But now I understand, that PPM is a way to gauge what the plant is eating, drinking, what its eating and drinking.

PPM is like doing blood work at the Dr. office.

Ha. Helped me. For sure!
Blessing to ya!

Grow more!


Looks like you’re in pretty good shape here. A lot of plants will eat up high ppm and not skip a beat. If you keep at it, you’ll eventually come across one that doesn’t. Just the way it is sometimes… Having everything dialed and reference materials handy is definitely the the way to go. But don’t get so consumed in that stuff that you ignore the feedback plants give you either.


Very well spoken…


I totally have the tendency to get consumed by new stuff like this - i jump into the deep end head-first without a thought until im being sucked down the drain. I do it with everything in life - it’s fun most of the time! I love to learn and for some reason I’m drawn to precision, as painful and tedious as it can be at times.

anyways - I plucked a new question out of the swirling mass over my head right now

Now that I have confirmed my water’s clarity, I am wondering about additives.
“They” say that RO removes everything but the water. Well, I dont have RO, but the ppm is so low (15) that I am wondering if it’s necessary to supplement Ca and Mg?

any thoughts on that?


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Probably, unless there is already enough in your medium. A lot of well amended soils will have enough calcium and magnesium, some won’t. But even if your water was 300ppm there’s no guarantee that elements in it would be mobile and available for uptake.


i assume that, as hot as FFOF is, ca and mg are available to the plant for now. whether or not the pH is allowing for it is another question.


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