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Ppm and ph rising fast in dwc

Perfect Sun LED

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You can check my second grow journal if you need more background.

I am su frustrated. I can't figure this crap out.

So, first, the plant was in a bottom feeding pot from Walmart. My stupid ass didn't pre-think the outcome of the bottom shape leaving room for pure water and holes for roots to grow down into, so algea grew. I am pretty sure this is what started the rising ph issue.

So, I cleaned everything, roots, container with peroxide and water 1tsp per gallon. 3% store kind. Then I filled a 5 gallon bucket up. Check picks really quick to see the pot it used to be in, and I sat that pot in the orange bucket.




They are in a 100% perlite. The roots hanging down are now in dwc with four air stones.

I filled the res with only 230 ppm (these are autos), vf-11, 29% peroxide 2mL per gallon (4 gallons of water in the 5 gallon bucket), recommended hygrozime (I think 10mL per gallon), oh, and a teaspoon of baking soda, so hopefully help stablise the ph longer. Oh, and drip clean.

Ph was 5.5 when I put the plant in, ppms 230. 2-3 hours later, ppms 330, ph 6.5

There is no more algea that is visible or that you can feel. No sliminess to the roots at all. WTH would be causing both PPMs and PH to rise? This means the plant is not taking up nutes, but you would think it would take some up even at 6.5, and while it was 5.5 and rising to 6.5

For now, I am going to ph it again to 5.5, then run all that 4 gallons through the perlite to clean the roots in that medium, to which it will empty in another bucket. I will then run it through again. I will then check the ppm and ph after running it through to see how much nutes it picks up in the perlite. I will keep doing that until the ppms and ph are the same after running through medium.

Then I will once again make a new res, this time with less peroxide, less hygrozyme, just a bit of GH at 1,2,3 parts, drip clean, and this time no baking soda. I will then Ph it if it drops before I go to bed, then check when I wake up and check both ppms and ph.

I am also going to see if I have the answer to why ppms and ph would rise so quickly in my Cervantes books.


New Member
Baking soda causes your PH to rise, not stabilize. Personally, I wouldn't use any pH adjusters unless they were specifically designed for growing. Baking soda/lemon juice, etc can cause reservoir problems like unwanted toxins, algae growth, etc in DWC. Soil? No problem, as it's more forgiving, but NOT hydro. Hope this helps. Peace!


Active Member
Baking soda was just something I tried. It's not in there now. Still trying to figure out what would cause both ph and ppm to rise.

i used to have ph problems in dwc with the nutes i was using the ph would drop to 3 after nutes were added but waited 24 hrs and was at 9 at that point i would use ph down and get it to a 5.5 and it would stay there till water change so after you add nutes wait 24 hrs and check ph and use ph down as needed not soda or vinegar.
go to your local hydro store and buy a bottle of ph up and ph down and use as needed


Nug of the Month: Feb 2014
hello Frenchy, here are some things that can be doing it in your grow.

Perlite is about a 7ph. Now usually it will not effect the water because its solid, however if it is crumbly from not being heat treated at the proper tempature then it would act as a ph buffer trying to always bring your water to 7.

To check dig down in the perlite to the middle or bottom or both and grab some kernels of perlite and see how easily they break in hand. if it breaks apart there ya go, it explains the rising PH and the ppm.

Another possibility is that inside the medium there is particles attached to the perlite that dislodge from the air bubbles constantly smacking them and jarring them.

Another possibility is your air stones are dirty.

TBH the first suggestion is most likely imo although it sounds goofy. crumbly improperly heat treated perlite.

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Just so everyone knows, the PH was rising quickly before I ever turned this into a dwc. Stones are brand new. The reason why the ph was rising so quickly was the algea. I fixed that. Ph isn't rising so fast now.

In 9 hours it went from 5.5 6.6--I can deal with that, and that was fresh res, only ph'd once. I ph'd it again and will see how long it takes to rise back to 6.2, if I catch it in time.

I'm not sure if the ppms are still rising.

Jimmy, i did a test with the Perlite for that reason. I put some in a dixie cup, put ph water 5.5, checked the next day, it was 5.6 or 5.7,so the perlite can't be the issue, I don't think.

he only thing that baffles me is why the ppm and ph both rose, usually it is opposite, ph rises, ppms go down, or if ph drops overtime ppms rise.

Either way, ppms rising is not a good thing. I will update and let you all know if the flush fixed that. It fixed the quickly rising ph, so far.


Nug of the Month: Feb 2014
Well another thing that can make ppm rise is when water evaporates. But you would have to have like 1/3 less water between measurings for that to be the cause.

I thought of something else that is possible for ppm rising and it depends on your nutes. Theres a few ways it could happen.

Ok so when you first mix up the water and nutes its possible that much of the nutes are not yet broken down in the water. Its kinda like when you buy fresh juice, youll notice its way thicker at the bottom. This could cause your ppm reads to be erratic in many ways:

1. most nutes are settled in the bottom and your water is being measured from top (or visa versa)

2. certain particles take hours to breakdown while others are instant. Just like if you put a rock of say lime into water, it would not raise the ppm or ph, however over a long long period of time it would do both. However if you put a bunch of tiny tiny pebbles of lime they would dissolve far more quickly becaus emore surface area touched the water, then if they were like grains of sand they will of course dissolve even faster!

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JJ, tap water ran through carbon filter, but my tap is only 40ppm and it is on the softer side, with zero chlorine according to test strips after filter.

Jimmy, that sounds possible, but with General Hydroponics three part series that is liquid? I mix it up well before I take a measurement.


Nug of the Month: Feb 2014
TBH I dont believe it is possible with the GH flora line.

Heres what i suggest ya do.

First off the more air and gyration the faster the PH rises. Should consider less stones 1 good one is all ya need.

Second off personally when i did dwc i just would set my water to 4.8-5.2ish then it would slowly rise and tbh i never touched it again. Never had a deficiency.

Third, just pretend you dont have a PPM meter lol.


Nug of the Month: Feb 2014
Well 200-300 ppm sounds ultra low. I mean usually plants that size people have like 600-1200

Nitrogen is basically always available so if it looks like nitrogen yellowing id say you simply dont have enough nitro.

However phosphorous does get locked out at roughly 6ph.

So if it looks like P deficiency then yeah lets worry about the PH and drop it lower so it has longer before it gos back up to the high 6. However if it looks like nitro deficiency then you just need more nitro.

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I thought the same thing, but when I put them on 700 the tips burnt a bit. These are autos, which I guess don't like very much nutes. Even the seed companies like the Attitude recommend keeping nutes low.

This is my first time growing them. What is odd, is both are the same strain, same feeding, yet one has stayed pretty dark green. I ended up putting that on in pure perlite hempy style, with an air hose in res. Basically, just drill another hole and poke an air hose in it.

I am more comfortable with hempy than dwc.

Then again, the one that is yellowing a bit on some leaves grew retarded. 3 leaves on one side, one on the other, so not uniform.

If keeping the ph stable and ppms low doesn't fix the hydro, I will bump the ppms up to 500 and watch for burn.


Nug of the Month: Feb 2014
Keep in mind the water will always rise or fall back to its natural state.

Still think ya shouldnt worry about ph so much and increase your nutes a little.

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I did have them at 360 for a few hours, but needed to add more water, so they are at 260 again. When I change the water after I see how long it takes ph to rise this time starting at 5.5 and to see if nutes drop at all in the next 10 hours, I will put them up to 400.

I'm just going keep reducing the nutes back to 5.5 after they raise to 6.5 or higher, depending when I catch it. That rise and fall should keep her happy enough to take the nutes she needs.

If after a few days, the nutes don't fall at all, and keep rising, I will then believe the roots are damaged, but I will just stick to he plan so long as they aren't slimey or don't get too dark.

Keep the ph in that 5.5 6.5 swing and hope nutes drop eventually. Might take a few days.
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