pH Crashes and EC Spikes in DWC - is this the issue?

razingthebar

razingthebar

Member
For anyone tracking this, my gains have been short-lived. I am able to stabilize the pH for up to 36 hours after adding Great White and hydroguard (hydroguard alone appears to do nothing - maybe it keeps things from getting worse).

Do people who use GW add it when they top-up? I've been changing the res with fresh nutes about twice a week and then topping-up with fresh water only to fight nute lock because the two strains growing in the same res have significantly different appetites. If I'm adding GW once a day, that seems like it would gunk up the system more than anything...

Here's a pic of the roots from a day or so ago.

I did get my H202 in the mail, but I'm on the fence about using it. I'm at the start of week 6 (Day 36) of Flower, and the buds are looking pretty decent, pistils on most are starting to darken and curl, trichomes are still clear - I'm hesitant to do something drastic this close to harvest.

I thought for a minute I might not be letting the chloramines evaporate (not letting my water sit long enough - I let it set about 18 hours). However, I tried letting it set for 24+ hours one time and had the same result as letting it set for about 6 hours. My thought was the chloramines were killing the hydroguard and GW (but for some reason not the pythium)...

So now I'm back to adding about 1.5ml pH Up twice a day to keep the pH in a normal range - otherwise it drops into the 4s. My next grow I may try a sterile res, but I"m hesitant to start using it this late into the grow...assuming you would use H202, I"m interested to hear thoughts about starting using it with only 2-3 weeks left. I think I can get there without it...

At this point my best guess on the pH issues: room temps in the mid-80s (750W equivalent LED in 4x4 grow tent); res temps in high 70s to low 80s. That's causing a bit of root rot, which is messing with the pH. Also, having two strains in the same res with very different appetites means if I'm feeding X correctly, I'm burning Y; if I'm feeding Y correctly, the nutes are leeching out of X and making the pH drop. I currently try to straddle so the EC rises slightly while burning the one strand only slightly. Also, having this all occur in such a small reservoir makes it prone to more drastic pH swings.
 

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Billy the Mountain

Billy the Mountain

Well-Known Member
Res temp in the high 70s to low 80s is a recipe for disaster. Continue with what you're doing for the last few weeks. Frankly your roots look pretty good considering the temps. You may not be so lucky with those res temps next time. Over 72f is borderline for dwc, 75f is danger zone.
 
razingthebar

razingthebar

Member
In case someone is following this to fruition: cal/mag was a big help. I did not know I needed to add it to my RO water - I thought it was optional, but for me it was not. My pH drops only fell into the 5.2-5.4 range after that adjustment. Still something going on, but manageable - I think it's tied to different strains in the same res and small res.

I will not grow multiple strains in the same res going forward. Not only the feeding issue (fried tips on one strain and the other underfed and leeching nutes), but now at harvest one strain is ready to go but the others not so much - I want to flush, but since all are in the same res it's like hitting a moving target.

SO, my big question of the night: Are these trichs ready for harvest? Or too clear still? These are the clearest of all my plants (one strain has all milk-white trichs, this is the other). Appreciate the thoughts.

Takeaway for others having similar issues: I still made it to harvest with all four plants (update to follow on yield), even with pH dropping into 3s and 4s daily and high res temps, etc. Don't give up, take good notes, learn from your mistakes - you'll get there, and the things that seemed like HUGE issues at the time will turn out to be great learning moments.
 

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70's natureboy

70's natureboy

Well-Known Member
We all knew that but your experiment confirmed it again. RO water needs cal mag to stabilize PH. Your weeds were tough enough to soldier through.
 
BurntByFire

BurntByFire

Active Member
razingthebar said:
Noob, but studying hard.

ISSUE: A couple days before the flip my pH started crashing from about 6 down to 4 (sometimes lower) in about 12 hours. EC/PPM would spike in same time period.

RIG: small (5 gal) DWC with top down and two air stones (air pump is outside the grow tent), Humboldt Seed Co. Magic Melon and Collie Man Kush (two of each) sharing same res, RO water and (prior to these issues) changing res about every 7-10 days. Lotus Nutrients (currently Bloom and Boost).

Day 12 of Flower as I write this. Plants look healthy overall (a little nute burn on a few tips here and there).

Right up until the flip I was running 1,100PPM (less than nute company suggestion) with pH only increasing slightly over time. About the time I noticed nute burn on the tips of only one strain the pH crash started and PPM spikes. I tried res changes and lowering the PPM, but still ended up with crashes and spikes. Roots are nice (no slime, no smell) and I'm using hydroguard (2ml per gallon), so I don't think it's root rot.

I have the chart from 420 Mag. that people keep posting, which suggests lowering EC and doing res changes until the issue stops. So far I'm down to 400 PPM and still having the same issues.

Then I saw someone quote this and wondered if this is the issue:

As plants uptake water they do not necessarily uptake nutrients at the same rate and as this occurs, the plants might be drinking lots of water but not eating much food. The result is that in a matter of hours, as the water is depleted, the concentration of the nutrients in the bucket can reach toxic levels. So it is critical to always under feed your plants in this system

Up until this started happening I was topping every day with nute water at a lower PPM to bring them down (e.g., if I wanted 800PPM and res rose to 880PPM over a day, I would add 600PPM water to lower the PPM back to about 800PPM). The quote above suggest that while the PPM was rising, some nutrients may have been consumed while others not, then when I added the nute-water top-up I was adding MORE of the nutes that were not consumed, raising those particular nutes to (maybe not toxic, but) bad levels which causes the pH to crash b/c the built-up nutes are acidic. In a sense, I've been chasing my own tail if that's right...

Is the cure as simple as topping up with plain, balanced water (no nutes)?

But maybe I'm over-thinking this one. (I also recognize I may have an issue caused by two strains in one res - if one wants a LOT of nutes and the other very little, that could be causing one to burn and the other to be deficient or at least leeching nutes back into the res.)

Many thanks for your thoughts
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AA7A4BCE-8025-478D-9473-F7FF59161AB6.jpeg
 
J

jambud

Member
Again, thanks for continuing with such detailed info on your grow/probs. Even when not many were responding it is very helpful even after the fact to read what someone else has done. I'm fairly new to DWC and do a lot of reading and lurking gathering information to help with my issues. Good Job.
 
Wastei

Wastei

Well-Known Member
You're overfeeding. Always start at 1/5 to 1/4 strength. You can always add more nutrients, flushing is a hassle.

I feed 350-400ppm max in soil. 500-700ppm in hydro, 0.5 scale. Don't go by recommendations. Read the plant.
 
O

Oxyrhina

Member
razingthebar said:
I thought for a minute I might not be letting the chloramines evaporate (not letting my water sit long enough - I let it set about 18 hours). However, I tried letting it set for 24+ hours one time and had the same result as letting it set for about 6 hours. My thought was the chloramines were killing the hydroguard and GW (but for some reason not the pythium)...
Click to expand...
Just a FYI, chloramine takes much longer than that when leaving water to sit out. That's why they started using it, it stays stable for much longer than chlorine. There was a study done that suggested when using tap water for moisture when rearing delicate insects to let it sit at least 14 days, 20 was preferable. So you probably were counteracting the hydroguard which is pretty pathetic to start. Check out Southern Ag Garden friendly fungicide, it's the same thing but literally 1 million times more concentrated. Better yet is Mycostop or to breed SA GFF or the combination.

Sorry I couldn't help with anything else but as was said, thank you for taking the time to document everything!
 
S

Schmuinki

Member
Thank you for your detailed notes. Also on first DWC grow, about 5 weeks into flower. Haven't had nearly as many issues as you but I've learnt a lot from reading your thread. Will be watching to see how it all turns out
 
razingthebar

razingthebar

Member
OK, so lately I've been dealing with deciding when to harvest. Recall, there are two strains in the same res. The one that has given me less trouble (the more indica-looking one) has the classic signs of being in the harvest window - white trichs, all red hairs curled in, etc. The other strain (more sativa-looking one) that has been giving me hell still has clear trichs.

I am at 85 Days since the flip (i.e., more than 12 weeks) and I haven't really noticed a change in the trichs on the problem ladies in weeks. So I do some research and it looks like some strains have trichs that never change from clear and some growing conditions can cause trichs to remain clear - likely also strain-specific. So I'm keeping that in mind.

The other problem is the difficult strain has had issues all along and the fan leaves have been yellowing and falling out at a rate far faster than the other strains. At this point, some colas have nothing bud buds and sugar leaves on them (at least in the upper part of the canopy), so I"m not sure the plants have enough fan leaves to process the light to continue to grow/mature.

I'm also now seeing a little discoloration on the little sugar leaves on the buds (again, this is only on the difficult strain, and only on some of the buds).

Lastly, maybe 10 days or so ago I thought I was going to harvest, and I started to ramp down the nutes in prep to flush for a day or two immediately prior to harvest. After reading and discussing with some folks here, I decided to let it go longer, so I ramped the nutes back up to "normal" levels. However, it appears the ramp-down (understandably) caused deficiencies which manifested mostly in the difficult strain, but also in a few of the fan leaves on the non-difficult strain.

See the picture of the fan leaf below - it looks pretty terrible actually. But this sort of crept up and stopped occurring once I upped the nutes (once I knew I wasn't going to harvest for a little while). The problem is, more fan leaves on the problem strain curled up and died (I presume the plant was pulling nutes from those leaves).

So again, now I'm left with mostly no fan leaves on the strain with the mostly clear trichs. See below for a pic of the trichs on the problem strain.

Some of the stems are starting to bow and break under the weight of the buds, even though I have many supported.

All things considered, I'm pretty sure I need to go ahead and pull them. I don't want to ruin the good strain (that has more yield) because I"m chasing the difficult strain that will never get any better b/c it has no more fan leaves.

So I started the flush this afternoon and plan to let it go two days, then harvest.

We'll see what happens.
 

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M

Moonmanyyc

Active Member
razingthebar said:
For anyone tracking this, my gains have been short-lived. I am able to stabilize the pH for up to 36 hours after adding Great White and hydroguard (hydroguard alone appears to do nothing - maybe it keeps things from getting worse).

Do people who use GW add it when they top-up? I've been changing the res with fresh nutes about twice a week and then topping-up with fresh water only to fight nute lock because the two strains growing in the same res have significantly different appetites. If I'm adding GW once a day, that seems like it would gunk up the system more than anything...

Here's a pic of the roots from a day or so ago.

I did get my H202 in the mail, but I'm on the fence about using it. I'm at the start of week 6 (Day 36) of Flower, and the buds are looking pretty decent, pistils on most are starting to darken and curl, trichomes are still clear - I'm hesitant to do something drastic this close to harvest.

I thought for a minute I might not be letting the chloramines evaporate (not letting my water sit long enough - I let it set about 18 hours). However, I tried letting it set for 24+ hours one time and had the same result as letting it set for about 6 hours. My thought was the chloramines were killing the hydroguard and GW (but for some reason not the pythium)...

So now I'm back to adding about 1.5ml pH Up twice a day to keep the pH in a normal range - otherwise it drops into the 4s. My next grow I may try a sterile res, but I"m hesitant to start using it this late into the grow...assuming you would use H202, I"m interested to hear thoughts about starting using it with only 2-3 weeks left. I think I can get there without it...

At this point my best guess on the pH issues: room temps in the mid-80s (750W equivalent LED in 4x4 grow tent); res temps in high 70s to low 80s. That's causing a bit of root rot, which is messing with the pH. Also, having two strains in the same res with very different appetites means if I'm feeding X correctly, I'm burning Y; if I'm feeding Y correctly, the nutes are leeching out of X and making the pH drop. I currently try to straddle so the EC rises slightly while burning the one strand only slightly. Also, having this all occur in such a small reservoir makes it prone to more drastic pH swings.
Click to expand...
The rule of thumb for any grow is 1 gallon per foot of plant just an FYI but very informative and I go no less than 5 gallon pail per plant
 
razingthebar

razingthebar

Member
ÒÒlegilizeitÒÒ said:
I found this awesome flow chart
View attachment 4748049
Click to expand...
I followed a similar approach, experiencing rising EC and falling pH. Chart says res change and lower EC. I did that all the way down to 0.6EC with the same results (only worse b/c some of the plants then started showing signs of nute deficiencies). I ended up raising the EC back up to around 1.0-1.5 and just dealt with the EC spikes and pH crashes as they came. Adding Cal/Mag helped with the RO top-ups. I was ultimately able to harvest all four plants, and am now curing. They were airy and fluffy for the most part, probably due to the temps being in the high 80s for a large chunk of flower. We'll see in a few weeks how they turned out.
 
ҖҗlegilizeitҗҖ

ҖҗlegilizeitҗҖ

Well-Known Member
razingthebar said:
I followed a similar approach, experiencing rising EC and falling pH. Chart says res change and lower EC. I did that all the way down to 0.6EC with the same results (only worse b/c some of the plants then started showing signs of nute deficiencies). I ended up raising the EC back up to around 1.0-1.5 and just dealt with the EC spikes and pH crashes as they came. Adding Cal/Mag helped with the RO top-ups. I was ultimately able to harvest all four plants, and am now curing. They were airy and fluffy for the most part, probably due to the temps being in the high 80s for a large chunk of flower. We'll see in a few weeks how they turned out.
Click to expand...
Are you using any organics? Those can destabilize the ph pretty easy
 
Mkultra81

Mkultra81

Member
Ive just come across this thread and i can tell you i was having the same issue as you on my last couple of grows. I like to veg my plants for a good 2 months + and usually top them multiple times along the way. Everything would go fine, i would head into flower and a couple of weeks in i would get exactly the same issue, ph dropping like a rock over night a couple of days after changing the res out. I couldnt figure out what was going wrong. On another forum i was advised that the pump i was using was nowhere near enough for the size of root system i was trying to sustain. I was using the tetra aps300 which i thought was more than enough for one bucket. Anyways, i went ahead and bought a commercial air pump and a batch of new cylinder air stones and have not had that issue once in the last couple of weeks at all. Everything seems to be forging ahead again. The size of pump didnt even enter my head whilst trying to figure out what the hell i was doing wrong. What size air pump are you using?
 
H

harvey_m

New Member
Trying to remember as much as I can from skimming all the posts in this thread, maybe I have a little I can contribute.

First thing is you need a lot more solution for the number of plants, but I think all of us here already know that. Just confirming it.

One thing I read repeatedly was about adding ph corrected ro water. That doesn't really make sense. PH is a function of tds, or ec. In other words, a super low ec or distilled water, it is going to take virtually nothing to affect the ph..and conversely, that ph has virtually no effect, because anything can alter it so easily. The higher the tds/ec, the more meaningful the pH is.

A little more on ph. When I was learning to grow, I read and followed the idea that the ph should always be some magic number, say 5.8 for example. But I almost immediately began to question that, once I realized everyone had a different "magic number", and especially once I read how different nutrients are available at different PHs. Once I began to let my ph swing, between 4.9 or 4.8 and 6.3 or so, my life got a little easier. No more pointlessly fighting it every day, and healthier plants.

A little on TDS/EC. When I was learning, I read over and over "anything wrong, take the nutes out and give them RO water", talk about garbage advice. Yet I probably read it a thousand times. What you'll learn is the behavior of the plants with repect to tds and ph, when to start the flush, etc, and then you'll figure out what they're actually taking up as far as nutrients and how that affects the ph. Once you figure that out, you'll know what to add. For example, if they pull the PH up in early flowering, or veg, what's something good to add? How about nitric acid, since they're probably pulling a lot of nitrogen at that point. Or when they're dropping the pH hard during flowering? How about instead of sodium hydroxide, add potassium hydroxide, since they're likely uptaking potassium. What you add to correct your ph matters.

A little on your solution temp in DWC. I've argued this point and been told that I'm giving "bad advice" for this, but I strongly disagree, based on experience. As you likely know, water temp and dissolved o2 are inversely proportional. But it doesn't matter in DWC if addressed correctly. Why? Because it doesn't matter if the water can "hold" the o2 when the bubbles are contacting the roots directly. You just need enough air. Not like a fishtank. Like water at a low boil. My 60 gallon dwc tubs would hit 85 degrees in the summer without any root damage. Some guys say that's just a fluke, or that I had exceptional sanitary processes, etc, but I never sanitized anything. Never added anything to the res to fight root rot. Ever. I even did experimental grows where I never changed the solution the entire flowering time, just topped it off until the flush. Almost no difference. Some guys change it every week! I grew in DWC for 4 years. If you're running one of those lowes/homedepot/etc containers that everyone uses, you need at least 6 of those long airstones, and 6 air pumps. Or aeration tubing and a commercial air pump. I know this is controversial and everyone says you need to have 68 degrees, but it flat out isn't true. You just need enough aeration. That's the reason I went to DWC in the first place, being able to run another light instead of the chiller in a tube sprayer system.
 
H

harrythehat

Well-Known Member
your problem is clay pebbles great for garden paths an that's about all.
they continually leach and will constantly change your EC and PH
you cant do anything this time live with it next time change your substrate rockwool is much better and a 50 mm net pot is ample substrate believe it or not. you can grow 8 foot trees in a 50 mm net pot yes its plenty big enough
 
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