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

Billy the Mountain said:

Water temp is crucial in dwc. 68f is considered ideal, 72f ok, 75f+ danger zone. I had to turn on my AC which I was trying to avoid. One heat wave was all it took to light the pythium fuse. Use a liberal dose of the hydroguard and great white bennies. Southern AG GFF is very similar to hydroguard but is literally a million times more concentrated. Ultimately, you have to get the water temp in check. Summer and dwc is bad combo for many.

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I use UC roots and no chiller. My water temps are about 72. No pythium, no algae, no nothin. UC roots works good.

razingthebar said:

Further update:

Changed res yesterday morning to 0.62EC and 6.14pH. Nine hours later it was 0.675EC and pH 4.75. Added pH'd water (no nutes) to EC0.55 and pH6.0.

Today at noon it was EC0.6 and pH 4.1.

Added pH'd water to EC0.5 and pH 6.0.

I can't for the life of me figure out why EC is going UP when it's already so low. Seems like an over-feeding situation by the rising EC and plummeting pH, but I'm at 250PPM/0.5EC in the 3rd week of flower, which is WAY less than everyone says it should be.

ALTERNATE THEORY: Any possibility the EC could be too low, resulting in a higher EC/nute content in the plant vs. the res, with the plants leeching nutes as a result of the imbalance, and the nutes being leeched are lowering the EC?

I could bump the EC up to 1.0 or 1.5, but even at 0.6 or 0.7 I'm seeing fried tips, EC raises and pH drops. Ordered some cal/mag should be here tomorrow, so will try that as well - seems like that would NOT be a silver bullet to fix all these issues though...

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I agree with your alternate theory as a possibility. This can happen and would throw the issues you're having as a result. Solution would be to carefully raise your ec mix at next feed. I'm not saying to do so but thats the fix.

Few things to consider...

Always use calmag supplement with RO water. (Which I saw you are now)

Always add calmag FIRST before your nutrients. (Unless you use silica then that goes first)

LED is optimized at higher temps around low 80s, so your tent temp is ideal for LED.

Water temp is an issue. Try wrapping something to deflect heat around buckets if possible. I have mine wrapped in reflectix and it does well. Also, know the air temp outside tent is being pulled into your water.

Air quality. If your air contains more CO2 pending on your environment than that could cause PH to drop or just poor air quality in general since you have air pump outside tent.

All of this can throw your PH outta wack, but ultimately IMO the problem has everything to do with you growing 4 plants in a 5 gallon rez. Especially 2 different strains that could have different requirements and needing different treatment. You'll be fighting PH until you change this. Everything else is a bandaid for root rot preventative but it won't help your PH imo.

Billy the Mountain said:

Water temp is crucial in dwc. 68f is considered ideal, 72f ok, 75f+ danger zone. I had to turn on my AC which I was trying to avoid. One heat wave was all it took to light the pythium fuse. Use a liberal dose of the hydroguard and great white bennies. Southern AG GFF is very similar to hydroguard but is literally a million times more concentrated. Ultimately, you have to get the water temp in check. Summer and dwc is bad combo for many.

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Since Southern AG is so much more concentrated, is it basically that you cannot use too much bacillus?

My Name is Mike said:

I agree with your alternate theory as a possibility. This can happen and would throw the issues you're having as a result. Solution would be to carefully raise your ec mix at next feed. I'm not saying to do so but thats the fix.

Few things to consider...

Always use calmag supplement with RO water. (Which I saw you are now)

Always add calmag FIRST before your nutrients. (Unless you use silica then that goes first)

LED is optimized at higher temps around low 80s, so your tent temp is ideal for LED.

Water temp is an issue. Try wrapping something to deflect heat around buckets if possible. I have mine wrapped in reflectix and it does well. Also, know the air temp outside tent is being pulled into your water.

Air quality. If your air contains more CO2 pending on your environment than that could cause PH to drop or just poor air quality in general since you have air pump outside tent.

All of this can throw your PH outta wack, but ultimately IMO the problem has everything to do with you growing 4 plants in a 5 gallon rez. Especially 2 different strains that could have different requirements and needing different treatment. You'll be fighting PH until you change this. Everything else is a bandaid for root rot preventative but it won't help your PH imo.

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I agree with all you said - especially the small res (live and learn). Didn't know to add cal/mag first, I was adding it after the nutes so I'll switch that up, thanks

razingthebar said:

I agree with all you said - especially the small res (live and learn). Didn't know to add cal/mag first, I was adding it after the nutes so I'll switch that up, thanks

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Good deal. I hope that helps stabilize your ph.

Something is happening...let's see if it sticks.

I got Great White (GW) in the mail yesterday, so mixed up a batch of nute-water to sit overnight in prep for res change today.

9pm last night: I left the res at 0.42EC and pH 6.2.

Noon today: 0.475EC pH 4.6.

Finished balancing nute solution, incl. 3ml/gal. cal/mag, then added hydroguard at 3ml/gal and GW at 1/8 tsp per gal. (roughly the 5gram for 10gal. per the bottle).

Changed res, increased EC slightly and balanced to 0.88EC (last res change I brought it up to 0.62EC and walked it down with plain water top-ups) and pH 6.2 - left to bubble.

9:00pm - good water consumption; was tough to get a steady EC reading, but right around 0.91; pH 6.6! I realize it's not great it went up from 6.2 to 6.6 in half a day, but my pH has been dropping from 6.2 to 4.2 in that same time period for almost a month...I hope that means the hydroguard and GW are beating the piss out of the root rot...

Added plain pH'd water to 0.8EC and pH 6.15. Time will tell...

So that was short lived...

9pm numbers were good (see above), by Noon the next day EC was up to 0.86 and pH down to 4.8. If Great White did anything, it was over in less than 24 hours...

I'm seeing purpling of the fan leaves on some of my plants (all the same strain) - not sure if it's a K deficiency or the other strain seems to have natural purples coming out around all the buds...

I topped up with plain pH'd water to 0.7EC, pH 6.25 at Noon.

9pm EC was up to 0.85; pH 4.4. Topped up to 0.7EC and pH 6.15

11am next day EC was up to 0.75 and pH down to 4.6. I've been adding about 2ml hydroguard per day just to try to stay on top of it - seems like you really can't use too much of that stuff....but it seems like it's just holding root rot back and not clearing it.

Looks like my next step is to switch to a sterile res and bust out the H202...none of the bennies seem to do anything much. Ordered some food grade, should be here in a few days.

My water temps are in the mid-70s (I've seen it creep up to 77 once) so that's likely a large part of the problem. Not much I can do to lower that based on my setup.

Air temps in the 80-84 range and RH 50-65%. Day 24 of Flower.

Buds seem to be coming along - but this being my first grow, I don't have much to compare it with.

Any chance you can snap a peek of the roots?

My Name is Mike said:

Any chance you can snap a peek of the roots?

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So, both the cal/mag and the Great White have a dark tint to them which takes my otherwise essentially-clear nutrient solution more brownish than otherwise. But I do think I have a pythium issue, and while there isn't a ton of slime I think I can see some.

Interestingly, the others don't seem to have an issue really - the only difference being these roots are directly below the net cup I remove to take readings and top-up. The light entering during that relatively small amount of time must cause the root rot to thrive more there...

This is about 60 hours after my res change that had GW for the 1st time (started using cal/mag just recently as well). For about the first 18 hours GW seemed to have leveled out the pH - which was great, as nothing else seemed to do much of anything - but the next day it was in the 4s again.

Waiting on the H202 to arrive. It seems to me the people that have problems when using H202 do not keep up with it regularly - at this point nothing else has worked...

hope this in a valuable insight; a big air pump can lead to a carbonic acid build up in the solution I've read somewhere I think it was in a post from RENFRO a really great user of RIU

Sorry to hijack this thread but it is somewhat relevant to me.

I have 2 plants entering week 2 - the PPM and PH are both rising rapidly. I startoff at 5.5ph at 1EC and the next morning its at about 6.0ph 1.2EC. From what i read in the 420chart above STATIC water level | RISING PH/EC means plant is leeching nutrients , raise EC. So i raised it from 500ppm to 600ppm yet it is still rising. That confuses me as from what i've read above, the plants are overfeeding and the EC needs to be lowered. There is much conflicting information where i read EC is too high and vice versa. I am also getting inward curling + yellowing lower leafs. This is my first DWC

Can anyone advise please

Changed out the res today - here's a pic of the roots in a near-empty res. To me, looks like some slight staining but a little slime here and there too...

This res change I went to 0.95EC; pH 6.2 w/ RO water, cal/mag, nutes, 2.5ml/gal hydroguard, Great White @ about 0.75g/gal. - in that order.

I don't think this relates to the pH crash issue - or maybe it does - but about a week ago the fan leaves on one strain (2 of the 4 plants) started turning purple - but only on the leaves closer to the lights (still 25 in. away from my LED (750w equivalent HID)). I first thought it was K deficiency upon doing some research, but where the leaves of two plants touched each other, I could lift up the top leave and the underlying leaf was perfectly green where no light hit it, but almost looks a burnt purple color everywhere else.

I have since raised my lights and done some LST to move the taller colas away from the center and down a little - looks like they continue to get purple, so maybe it's just the strain, but it does look like they're stressed in some way. I guess we'll see...buds still developing nicely - the other strain is having no such issues

Here is data of my rez starting to drop. Been looking for a trend. I flushed on Day 84 as you can see the reading that day before flush was 4.8. Seems like each time I add some nute, ph drops.

Today is Day 92, PH dropped to 5.1 from yesterday after adding PH up last night to balance it. Drop came after I added hydroguard. Everything else seems on point.

Sharing as it definitely happens to some of us as well.

BTW, I don't see slime in your pic. Roots actually look good.

Here's some data on the purpling issue - not sure if related to pH drops, EC spikes. This only happens with one of my two strains. They are both supposed to be indica-dominant hybrids, but one is short and bushy (indaca-ish) and the other tall and lanky (sativa-ish). This is the taller, lankier strain (Collie Man Kush, Humboldt Seed Co.).

The first pic is from a cola on the same plant but trained further away from the center of the grow (i.e., less light). Nice and green (some fried tips, yeah - but not bad for what I've been battling twice a day for over a month).

Other pics are from same plant, cola closer to the center of the grow (and maybe an inch or two higher). The purple looked like it was almost sprayed on. One of the plants had a perfect green imprint of another fan leaf when the light didn't hit it directly - the rest was entirely purple. Keep in mind I'm using an LED (some purples in the background, but you should be able to see the green splotches vs. the purple).

I thought it might be K deficiency, but the light "sunburn" thing makes me thing it's maybe light stress...or maybe it's typical for certain strains to do this? It seems like it would impair photosynthesis...

Yesterday I raised the lights about 3" and trained the taller colas a little further away from the epicenter

Appreciate any thoughts.

On the positive, after the res change today EC rose by only 0.05; pH went up from 6.2 to 6.7. Topped-up with plain pH'd water and we'll see tomorrow.

Tough one since sometimes purpling can be genetic. Try to rule that out first. If you get some indication it's not genetics, potentially it's a phosphorous deficiency or your temps dropped to low. This can be mistaken for PH issues but unlikely

Do you get a 24hr read on your temps? What was lowest it dropped to at lights out?

My Name is Mike said:

Tough one since sometimes purpling can be genetic. Try to rule that out first. If you get some indication it's not genetics, potentially it's a phosphorous deficiency or your temps dropped to low. This can be mistaken for PH issues but unlikely

Do you get a 24hr read on your temps? What was lowest it dropped to at lights out?

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Yeah, sorry I meant to post that data.

Temps range between 75-86F; RH 55-65% (up to 72% once when my dehumidifier filled up). It's toasty in there, I don't think it's low temps.

Will keep an eye on 'em

Day 26 of Flower for point of reference

could the purple response be a phytocrome response to full spectrum LED?
to have better purple expression I used cold temp during light out in the range of 16-18 C between other things... but having such big sway in your reserve could mean P isn't absorbed at the ideal rate...

CBDbear said:

could the purple response be a phytocrome response to full spectrum LED?
to have better purple expression I used cold temp during light out in the range of 16-18 C between other things... but having such big sway in your reserve could mean P isn't absorbed at the ideal rate...

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Good question. I'm definitely running at higher temps.

Two Part Update:

Purpling: Attached is a photo I snapped today that shows the negative outline where a fan leaf was laying across another fan leaf. Where the fan leaf covered the lower one, the lower one is green (but otherwise all purple). That makes me think it's tied to the light. It also started on the plants that were closer to the center and higher up, but has been spreading to (or at least showing on) the other colas from the plants of the same strain. Nothing like that on my other plants. Maybe it has something to do with the high temps and light...

pH Swings: Some good news! Yesterday I changed out the res again. Pre-change it was 0.72EC and 4.6pH. I added cal/mag, nutes, hydroguard and Great White. Left it at 0.93EC and 6.2pH.

Last night it was 0.97EC (very slight compared to prior EC spikes) and pH was 6.7! It went up instead of down for the first time in a month. I added plaint pH'd water to 0.82EC and 6.5pH (left it a little high since it always crashes down into the 4s).

Today around noon (24 hours after res change) it was at 0.84EC (very slight compared to prior EC spikes) and pH was 6.2! That's the first time in a month (since just before the flip) that pH has remained stable (or even anywhere close to stable). Added plain pH'd water again to 0.715EC and 6.2pH. We'll see if it holds...cautiously optimistic.