DWC pH, EC & Temp Data

[lord_haze]

Hi
Started a new dwc for the summer, now they are still in the 8l starter bucket and pretty small (~5cm - will be transfered to 60l bucket next week)

I started recording some data, wanted to share and ask some questions

- around 08:10 my (small, ~15W) cooler starts, so there is additional movement in the water
- blue is the watertemperature, orange the air temperature - around 11:30 the water is warmer probably due to my (way) too long, and black tubes from the cooler, will fix this soon
- around 17:00 i opened the window, that's why ambient drops and (imho important!) the temperature of the air that the pump delivers in the tank is cooler
- nutes are Advanced Nutrients Sensi Grow, some Canna root juice and a bit HCl to counter
-cooler stops around 20:00, it's set up to (try) to keep it between 20...22°C

That day i didn't add nutes or water, EC is more or less stable:

so my questions are:
- Why is the pH reacting so (crazy?) much to the air temperature that the bubbler delivers and not to the water temperature itself? (7:30 it gets warmer, 17:00 it gets colder, both times pH goes down :O )
- Why is the pH reacting so (again crazy?) much to the start of the water movement around 8:10?


If there is interest I'll keep updating whats going on and adding pics of the setup once it doesn't feel emberassing anymore
(cooler tubes, tools laying around, ect. )

Cheers
l. Haze

P.S.: they are indoors but just sunlight right now, they'll move to the balcony next week

 

[Creeperpark]

Interesting project friend. I thought using Advanced Nutrients you don't have to worry about the pH. Have you used these nutrients before?

 

[zachrockbadenof]

Interesting project friend. I thought using Advanced Nutrients you don't have to worry about the pH. Have you used these nutrients before?

is that true about advanced nutes?? i use GH nutes, 3 plants in hydro, 1 plant has a steady ph, but the other '2' plants are wild- i can adjust it today to 575/580, the next day its 5.20, or maybe 620- the water is changed every 2 weeks, the ec is not crazy high, but getting a steady ph is tough...

 

[Douglas.Curtis]

So... DWC does best when the res temps stay between 65F(18.33C) and 69F(20.5C). Below this temp and nutrients have difficulty flowing. Above this temp and you're looking at serious biological issues happening.

Should you be unable to understand why your res temps are going above 20.5C, you would have a significantly easier grow if you switched to a 'Roots-Out' system like E&F, drain to waste or any other intermittent watering system. These systems handle healthy plants up to 80F(26.6C) temperatures.

 

[lord_haze]

Thanks for the input!
I did use the Advanced Nutrients last year with my tomatoes and did not measure pH. Things were ok, I even had temps up to 30°C (86F) during hot weeks on the balcony. I guess I was lucky there were no bad bacterias growing.
But this year I'm adding an auto malawi x NL5 and want to monitor what's going on
I'm also developing a small peltier cooler (which I'll show once ready ) to keep it cool.

But clearly measuring pH once or twice per day on random occasions will potentially give very different results.

What I'm trying to understand is how do the pH buffers work and what are the chemical mechanisms and dependencies still at play.

I added some water today at around 9:00. I'm usijg RO water, not planningto change the water btw, worked well with the tomatoes last year and i want to verify it's not necessary.

todays plot:

I added some shielding frok the sun forbthe cooler tubes and the reservoir, lookong forward to seeing if it fixes the pH swings in the mornings and it was more of a sensor problem (placed to close to the wall that heats up from the sun?) or stilp correlates to the air temperature...

 

[negative37dBA]

If I read correctly you are in only 8 liters now? Less water equals more ph drift. A larger volume of water will not tend to drift as much as the tiny 8 liters you have if that's correct.
Even if you are checking only at random times there should be no significant difference in ph reading. If there is something is off. I monitor mine 24/7 with a Bluelab and the most I see is maybe a .02 change in a 24 hour period. If things go acid real quick then you have issues. Time to change water and start fresh at that point. You do regular water changes? What do you use now to adjust your ph to the right range? I actually employ a ph doser into my system to keep it EXACTLY where I want it. I turn it off from time to time to allow for as bit of drift because it allows uptake of diff nutes. But not to much drift.

 

[negative37dBA]

You ph monitor should not change reading because of temperature...What kind do you use?
I have a bit of exp with water...5 years now and not a ounce of dirt at any stage of growth has been used....growing 24/7/365.

 

[lord_haze]

Great to see all the experienced people here
It's a small 8 liters reservoir right now,yes. I'll transfer to the big 60l next week. Really curious to see how stable things will be then.
I used Canna ph up/down to set it up after the first nutes ,which is HCl and KOH. But the EC was rising quite a bit after adding it, so i really want to avoid having to adjust all the time! (Also avoiding water changes due to salt build up).
My Sensors are from Atlas scientific, both EC and pH are temperature compensated, but maybe the temp sensor placement in the small reservoir is not ideal. I'll make a small holder for the big tank to keep them together and centered i.e. away from the wall and air inlets.

 

[lord_haze]

You ph monitor should not change reading because of temperature [...]

Yes, it has a temperature compensation.
But I'm wondering if what I'm seeing is dur to Sensor placement and a delayed temperature reading (which is used for the compensation) or if there Is something going on due to the change in air temperature, e.g. change in CO2 uptake which moves the pH around...

 

[negative37dBA]

you say you want to not do water changes to avoid salt build up? Is that correct? Why would that happen? Its pretty common to do water changes once every week during all cycles of growth. Maybe I am missing something because I dont see how changing the water will cause salt build up...what salt are you talking about?

 

[zachrockbadenof]

you say you want to not do water changes to avoid salt build up? Is that correct? Why would that happen? Its pretty common to do water changes once every week during all cycles of growth. Maybe I am missing something because I dont see how changing the water will cause salt build up...what salt are you talking about?

i thought a water change should be done once or twice during the grow, not ever week...

 

[negative37dBA]

i thought a water change should be done once or twice during the grow, not ever week...

I mean to each his own but common practice is every week fresh water and nutes. Help prevent things from going sideways. That can happen very quick in hydro.

 

[zachrockbadenof]

Help prevent things from going sideways. That can happen very quick in hydro.

i have not had that problem, but for sure i have heard others have problems... maybe because my water temp's range from 63-66F i can get away with a longer change of water... maybe , but i'm not sure...

 

[lord_haze]

you say you want to not do water changes to avoid salt build up? Is that correct? Why would that happen? Its pretty common to do water changes once every week during all cycles of growth. Maybe I am missing something because I dont see how changing the water will cause salt build up...what salt are you talking about?

No, sorry to be unclear:
I want to avoid frequent water changes, actually I'm not planning to do any
I am justifying this by not adjusting the pH frequently by adding acids and bases which I understand will create salts sooner or later? At least every adjustment will also up the EC, so sooner or later the water would need to be replaced in order for the nutrient concentration to be high again.
IF things like bad bacteria growth happen then sure, I would change the water! But I am really lazy for that and prefer to understand and possibly control the risk factors of things going sideways.

So today I see two pH swings:
First one peaks in the morning around sunrise, not sure if that's the plants night/day cycle, would be nice to study in a more controlled indoor environment
Second one is clearly due to the cooler operation, but I don't understand why it's doing what it's doing

 

[negative37dBA]

Without any water changes how are you planning on keeping water chemistry correct? How are you planning on keeping the nutrients at the correct ratios? How long have you been growing in hydro? You talked about your water temps being as high as in the 80's... You said you were trying for 20-22c that's over 68 plus...barely on the high end of where it should be. It needs to be lower. Mines sits at 65 constantly.
In the end you can do whatever you want. When you ask for advice and don't take in don't be surprised if you quit getting it...
Hope it goes well for you.
Peace, negative.

 

[Ca++]

The first pic suggests the cooler was turned off at 16:45
The second pic is fudged, as you set the tank at about 08:30 it seems.
The last pic looks like the cooler ran 12:00 till 16:00

The suggestion here, is the cooler not being on a timer, and effects the pH probes function.

I'm lacking variables, so drawing assumptions from readings, taken with kit I know nothing about. It's difficult for any of us to get a holistic understanding of the job.

 

[Douglas.Curtis]

Changing nutes each week, or every 2 weeks, is a mfg's wet dream. It sells a LOT of excess nutrients.

Fill res with pure r/o
Add nutes to MAXimum desired ppm
Add pH UP to reach 5.4
Top off with pure r/o (daily) to the same level (Take readings at this same point each day)
pH will rise gradually as plants use nutes (res size vs. plants/lights determines how fast it changes)
When pH hits 5.9-6.1, add nutes back to beginning ppm (pH will be 5.4 without adjustment)

A week before flowers quit physically bulking out quit adding nutes back and just plain r/o only till finish.
Your goal should be to have transpiration rates stay the same after flower physical bulking quits. The plants switch to oil production and their nutrient needs drop significantly. Should your transpiration rates drop too low for too long, you can bet you've impacted your end quality with overfeeding.

You WANT the gradual pH swing, it not only assists with nutrient uptake it also increases terpene/cannabinoid complexity. It's a natural result of enzymatic activity and pH, and can be easily tested. The steady pH clone will be more plain and flat in taste/aroma/high vs. the varied pH grown.

 

[lord_haze]

@negative37dBA , please don't get me wrong I'm taking all the advice I can get and will implement it as I see fit - but I also have the goal of making the dwc growing experience as easy as possible and am willing to try things that some might find too risky. I did change my cooler settings to keep the temperature lower: starting at 21°C/69,8 and stopping at 19°C/66,2F. With that I'm covering depths of ~1m during warmer months. I know cooler is the standard but I'm trying to see which amount of cooling power i really need, and if something goes wrong what that will look like.

(data is from Germany: https://www.dwd.de/DE/leistungen/kl...f/ksb2011_art2.pdf?__blob=publicationFile&v=1 )

My expectations are that if temps are not too high for too long and air/oxygen supply is steady then there will be no chance for dangerously bad bacteria growth...
But that's just based on 3 seasons of hydro (1 EF, 2 DWC) - (but without any cooling).

Also I expect the AN nutrients to keep pH in balance for me. After reading their own story it seems the tech-details are proprietary, so I guess all that's left is some reverse engineering just for fun.

How Advanced Nutrients pH Perfect Technology Helps Growers

How Advanced Nutrients ph perfect technology gives you the best ph level for hydroponics

www.advancednutrients.com

They they the lock-in should be at 5.6 !

The last two days I wasn't home and didn't touch anything. No water added, no nutes added, no cooler operation as is was cold enough.
First night the pH is going nuts, rising for some hours and then drop... maybe a component of the buffer/chelates was triggered?
Second night pH is rising very little and coming back slowly in the morning

Tonight I changed the EC-Probe from a K10 to a much better suitet K0.1 and double checked the EC with another meter. It was sitting around 800 with the better accuracy.
I also added the recommended 2ml/L of nutrients and now I'm at pH 5.59 and EC 1.8
Let's see how the night goes and hopefully I'll find the time tomorrow to transfer them to the big 60l container.

@Ca++ The cooler starts now at 21°C and stops at 19°C (was 22/20), and probably the additional circulation has an influence on the sensor. Hopefullly this will be much less in the bigger container.

@Douglas.Curtis seems straight forward whihc nutrients do you prefere?

 

[negative37dBA]

Douglas.Curtis knows his stuff and his poop...lol. He will get the joke.

 

[Douglas.Curtis]

DWC with base nutes is definitely stupid simple as I outlined it. Any additives will mess with the pH swing and you'll get a sub-par result. Basic hydro I prefer MaxiBloom, epsom and calcium acetate for amazingly complex terpene and cannabinoid profiles. It's AMaaaazing what straight nutes without additives can produce.

If you're using AN pH Perfect nutes then I would expect problems with full nutrient uptake without overfeeding, and less complex flavors/smells/cannabinoids.