DWC PH issues: Ph dropping like a rock - Please help

[JohnC]

Well, even with the wild PH swings, the plant looks OK. I mean, I don't see any deficiencies or toxicities in the leaves. Would you all agree?

I guess I really have no choice but to add copious amounts of PH-Up each day to keep the PH in range.

[Jason]

Those girls are beautiful. You will be rewarded at harvest.
Ranging pH insures good feeding from the res. As long as you control it to range and not rest at a level too high or too low.
Looking good!

[Xcardplayer]

HOw often are you changing water? It might help alot to change weekly.

[JohnC]

I usually change the reservoir weekly though this past week I've changed it twice.

[JohnC]

Good morning, fellow growers. Another update.

Yesterday evening, before lights out at 7:00 p.m., I topped off the reservoir with RO water and adjusted my PH to 6.4 (knowing that it would drop overnight). PPMs were measured at 600 and EC at 1.2.

Soon after lights on at 7:00 a.m., I took my morning measurements: PH dropped to 6.1, PPMs increased slightly to 610, EC remained stable at 1.2, and my water level dropped overnight about a half-quart. I topped topped off the reservoir with nutrient-enriched tap water. The plant itself looks fine with no apparent deficiencies or nutrient-burn. She continues to gain in height each day.

So according to the chart: Water level falling, EC static, PH falling = Res change plus a change of EC. Lower EC if over 1.4, raise EC if lower than 1.0

So the way I understand the chart, I guess I need to do a res change but keeping the nutrients at their current level? Tomorrow (Sunday) is my normal reservoir change-out day, so I'll wait until then to do it. Tonight, I'll check the plant again prior to lights out tonight at 7:00 p.m. to see how the day went.

[GanjaGed]

Be careful with the chart, you have to apply some reality to it also.

So far from what you've posted, it seems to me you have either 1 of 2 problems or a combination of the 2

• High CO2/O2
• Low PPM

Both of these will cause what you're experiencing.

For the high CO2/O2 issue, which if I read right is likely caused by heating and corresponds to the time the issue developed is an environmental issue that may be hard for one to fix in many circumstances. Also without some kind of testing it's hard to quantify. Things that can address such an issue are:

• Change the source of the pump intake air. Such as fresh outside air.
• Move the pump higher. CO2 is heavy and sinks
• Decrease air flow into the reservoir.
• Increase reservoir/solution volume
• .Change aeration method, waterfall etc.

Now the PPM is a lot easier to fix since you can control that simply.

In a perfect tank you want the PPM's to remain steady while having falling water volume and a drifting PH. This becomes almost impossible to maintain as one adds more than a single plant to the same res and even harder with multiple strains, because everything is almost certainly going to feed at different rates/levels.

It sounds like you've got the PPM really close, so for now, if it was me that's the level I'd go at, maybe drop it to 575-590 but that's a dialing in process that can be addressed after the issue is fixed, so I'd stick with the 600 ppm for now as long as no burn occurs. In the end it's better to be a bit high than a bit low.

If it was me, at this point, if I'm understanding what's happening I would:

Mix solution at ~600 ppm

Quick check that PH was between 6-7. Yes that is high but we already know it's going to drop and the idea is to add little or ideally no PH adj.

Add air stones etc and let it run till the next day. Nothing at this point is going to seriously harm, let alone kill the plants.

The next day I would check PPM, PH, Water Level and adjust from there.

My hopeful readings, based on what's been going on would be a slightly higher PPM, PH in the 5.5-6.5 range, and lower Water Level. If those factors are correct I would:

• Top off Water
• Check and record PPM and PH
• Add nutes. I would do this in stages. I'd be looking for a slightly lower PPM (550-590 likely) that brought my PH in range 5.5-6.5 (ideally 5.8-6.2) The point being to adjust the PH with nutes instead of PH Adj. If I hit 600 PPM and my PH was out of range then add Adjusters. This also is dependent of the nutes you use, some, Silica for example, raise PH and others lower PH. Also Water quality will change how PH is effected because of Buffers. It's about finding the sweet spot.
• After that I'd let it run till the next day and check again.

Keep in mind, atm, it's possible you have 2 issues so fixing one is not going to completely solve the problem just lessen it and then only in relation to how much it's a contributing factor. After time you'll get to know where your numbers will be with a fresh solution. For example I don't check my PPM/PH at all until the day after,. It takes time for the res to stabilize, everything to fully mix, interact with the roots/bio of the tank, become fully aerated etc.

Anyways, that's how I would proceed myself, best of luck, and looking forward to the harvest!

[JohnC]

Good evening ladies and gents. Here are tonight's numbers at lights-off:

Air Temp: 69
Water Temp: 65.6
Humidity: 29
PH: Dropped to 5.7, added 4ml of PH-Up to reservoir to get PH to 6.2
PPM: 630 ppm prior to topping off with RO water; after top off: 620 ppm
EC: 1.3 prior to topping off with RO water; after top off: 1.2
Water level: Dropped another quart in the last 12 hours

[Jason]

5.7 is good. Let it drop to 5.2 or so before adjusting back up to 6+
You seemed to have a slower swing with the tap water.

[Xcardplayer]

Im guessing you are useing ph up and down to much, 5.7 5.8 are perfect numbers, i would let them naturally rise to 6.1 or 2 before i even considered touching.

[JohnC]

Good morning, folks. Here are this morning's numbers, soon after lights on:

Air Temp: 72
Water Temp: 67.8
Humidity: 26
PH: Dropped to 5.9
PPM: Dropped to 610
EC: Stable at 1.2
Water level: Dropped a bit more than a pint overnight

Sunday is my normal reservoir change-out day, but since I just changed the reservoir this past Wednesday, I think I'll be safe enough to let it go until next weekend.

Well, I think this thread has run its course. In summary, I have something driving down PH each night. What that is cannot be determined. Switching to tap water helped limit those PH swings but I still have no choice but to use PH-Up each day to keep the reservoir PH within range. I guess whether I'm chasing the PH upwards or driving it downwards, as long as the PH stays and varies within the range of 5.5 to 6.5, I should be OK. At least I got my air and water temperatures in a better range thanks to the use of the "foot warmer" heating pad.

Thanks everyone who responded and offered help.

[Paracelsus]

totally disapointed (as I know you must be) that you didn't lick this thing. I'm 3 threads in and I don't know what happened to your plant and DWC system

[Madman960]

'm on my 1st DWC grow and I let my ph swing from 5.2 to 6.8. It's my understanding that plants uptake different nutrients at different phs. So far so good.

Happy growing.

Madman