Huge ph swings!

[Bassman59]

I'm a bit worried. I'm doing dwc, ro water, 1/4 nutes in early stage.

I'm seeing PH swings like mad.

I ph test and see 7.0-7.5, have even seen an 8.0

I ph down, get 5.8-6.3, and 12 hrs later it's 7.0-7.2 again!

what causes such huge swings when there has not been a feeding for 2 days or more and only 1 plant with just 2nd set of true leaves coming?

 

[TorturedSoul]

Faulty pH meter? Probe needs replacement? EMI/RFI interference if you are using an AC-powered one? Your plant is hungrier than you thought and is consuming the phospheric acid in the pH down at a voracious rate?

Usually something nasty growing in the reservoir would cause the pH to tank instead of rising, so that isn't likely to be it.

 

[Bassman59]

new meter, calibrated, dc.

The one plant in 6 gals res is on 1/4 nutes with only 1 set of leaves and 2nd set just a cpl days in. I mean the plant is only 2 weeks from germ so I wouldnt think it's eating much.

 

[TorturedSoul]

I wouldn't either. And a six-gallon DWC reservoir is pretty small for a cannabis plant but that wouldn't be an issue for a seedling.

What kind of meter? If it's a pen-style, grab a sample and take it out of the GR to test it. If it's a benchtop that operates off of AC, shut down your lights and see if you get a reading closer to what you think it should be. (A poorly-shielded electronic ballast or power supply can screw with them.)

Hey, aren't you using GO nutrients? Seems like I read about some slime when I glanced at your journal. Pretty sure I read on GH's site (blog) that using GO in DWC can be problematic because of the aeration methods that most people use. Something about causing microbial life to grow. Might be that some of it (if you have some growing, of course) is digesting the nutrients which is causing the pH to climb. IDK.

Speaking of which, just how organic is GO? What do they use for pH buffers?

 

[Bassman59]

It's a pen style. I always take it out of the res then test. But the last few tests have been in the closed room the gr is in. I only tested it 2-3 times in this empty closed bedroom the grow tent is in.

I stopped using the GH liquid nutes when I saw that slime. I also did a complete drain-replenish along with a full wipe down of the tub and all feed tubs, pump, etc. I may not have cleaned it perfect however. Afterwards I refilled with ph adjusted r/o water (store bought).

 

[Bassman59]

jeebus, 3 hrs ago the ph was down to 5.8, now 6.2.

That just seems huge for 3 hrs.

and facking water temps hit 86f

 

[Caregivers]

Water tempatures that high will cause all kinds of nasty stuff to start growing in your bucket, especially if you using any kind of organic nutes. It is best if you keep your water temps down around 70 or so in order to avoid unwanted growth. Algae tends to bump PH to unhealthy levels.

CGs

 

[Bassman59]

Water tempatures that high will cause all kinds of nasty stuff to start growing in your bucket, especially if you using any kind of organic nutes. It is best if you keep your water temps down around 70 or so in order to avoid unwanted growth. Algae tends to bump PH to unhealthy levels.

CGs

shat. Well I stopped the organic nutes and went with the SH micro/grow on 1/4 feed two days ago when I did a drain/clean/replenish of the tub.

I added a 1 gal container (sealed) of ice to the tub a while ago and the temp has dropped 6 degrees so far. But I feel like this is one thing that may be nigh impossible for me to get down into the mid 70's once there are 3-4 huge rootballs in the tub since they wont be happy with laying down over ice! I cant afford a chiller for at least a few months I'm sure.

hohum

 

[Maer]

shat. Well I stopped the organic nutes and went with the SH micro/grow on 1/4 feed two days ago when I did a drain/clean/replenish of the tub.

I added a 1 gal container (sealed) of ice to the tub a while ago and the temp has dropped 6 degrees so far. But I feel like this is one thing that may be nigh impossible for me to get down into the mid 70's once there are 3-4 huge rootballs in the tub since they wont be happy with laying down over ice! I cant afford a chiller for at least a few months I'm sure.

hohum

You need a res chiller, large swings in root zone temps are detrimental to growth rate.