HYDRO Water acidification with plants in flower - air pump inside the growing space

[FlyingDutchPaddy]

morning update:
last night before lights out, pH was 6.4.

I left it there thinking the pH drop would return again, but less dramatic.

turns out this morning just after lights on - pH = 7.4

it has gone up.

from reading on pH drift, tending upwards is a good sign....

Have adjusted it down a bit... 6.3 now.

also observed the water being murkier now after a night... i can only assume that that is the voodoo juice and sensizym at work.

ppm is 1090 after adjusting the pH.

 

[Toker1]

Sounds like things are getting better now. Remember to keep the water temps low. That’s the only way to avoid future rot.

 

[MadMike]

I'm considering moving to rdwc for my next grow. (Hand watering Coco has just become too much for me.) Your trials and tribulations are super helpful to learn from! -- Subscribed.
I'm pretty curious about the water temp since that might be an issue for me in the warmer months. You might consider getting a cheap aquarium thermometer and dropping it in there to confirm the temp. I have an infrared thermometer gun and I use it to read everything in my grow room, and tons of stuff around the house generally. A great weapon to add to the arsenal.
https://www.amazon.com/gp/product/B00837ZGRY/ref=oh_aui_search_asin_title?ie=UTF8&psc=1
I have the 774 model.

 

[FlyingDutchPaddy]

Hey Mike, glad to have you along

After 2 days away I was fearing the worst for my plants... turns out there was nothing to be afraid of...
Just before I left, i pH'ed to 6.1 'to be safe'.

pH at 6.0
ppm = 1150
when I came back.

water was much clearer as well.

A chart I found a few days back on 420magazine about water level/EC/pH: https://www.420magazine.com/community/gallery/ph-ec_chart1-jpg.1609412/
it would appear that my plants are releasing nutes...

as water level is stable and pH is fairly stable, but ppm (EC) is slowly rising... i may need to add something to the water to raise the ppm. (I have epsom salt that could do it, would increase the Mg content as well)

i can understand why the water level is fairly static, I've trimmed a fair amount of roots away that were affected by root rot.

a quick check of the roots of both plants did reveal that new roots were growing, and so far the roots look good - no browning from rot.

 

[FlyingDutchPaddy]

Update!

pH has been dropping much more slowly since water change & system clean - good thing.
yesterday I got a 3m long 8mm air hose to connect my air pump to outside the tent.

have a feeling that the makeshift 4mm tubing that i ducktaped together was a bit small for the air pump - pump felt much warmer to the touch compared to running with the (normal fit) 8mm hose as it it now.

Lesson here is: a too smal air intake hose -> more work for the pump to suck in air -> warmer air that gets bubbled into the water!

Speaking of which... i suspect that having run with that smaller air intake hose has had an adverse effect on the water - roots are still looking well and growing but the water doesnt smell as good as before - has a more earthly smell to it.

will need to change water & clean system this weekend again.

had an idea I'll have to work out / construct some time:

a bucket with a length of air tubing thats cooled by water in a water bucket or champagne cooler.
rough sketch attached.

pH is 5.8 , ppm = 1160 before lights out.

 

[Toker1]

As you put warm air through the tubing, what is keeping the water cool in the sketch?

 

[FlyingDutchPaddy]

that water....

would lose the heat by convection to the surroundings...

and you could insert a frozen water bottle in it...

the water my warm up slightly, but the air should be cooler going out than it came in.

 

[Toker1]

Most people use frozen water bottles because they won’t leak water into the reservoir. That can throw off PH and EC/TDS.
This is not the most efficient way to cool the water down. The centrally located frozen water bottle allows warmer water to exist on the outskirts of the cooling bucket. My suggestion would be to use ice cubes distributed through out the cooling bucket’s water. This will improve your cooling capability.
If you insulate the bucket, this can further improve cooling efficiency.

 

[Obi-Wan]

If you coil a longer length of air line in the bucket to cool the air you will achieve cooler air in your bucket but your pump will work harder and produce a lower pressure through the stone. You may need to go to a larger pump to achieve the same air flow.

 

[FlyingDutchPaddy]

ice cubes would certainly be better at cooling the airtube in the bucket more uniformly.
but i think its more practical to use a frozen water bottle - much easier to replace and doesnt become part of the water already in the bucket.
i think using icecubes would generate more work to maintain the cooling bucket than frozen water bottles. (emptying out the excess water).

even so, the air should cool down as it passes through the tubing in the bucket and be colder than when it came in.

i'm looking for a 'simple, lazy' way to cool the inlet air before it gets bubbled.

 

[Toker1]

If that’s the route you want to go... why not just get a water chiller? Wouldn’t water bottles just be more work with limited benifits?

 

[LurkingInTheGrass]

Clear airline or opaque?
(I don't recall if it had been previously mentioned)

best thing I did was change out clear air lines for black ones

 

[FlyingDutchPaddy]

longer air tube -> bigger air pump; i get that.

tube itself is 'clear', but the part going outside the tent has been taped up in ducktape to be opaque to light.

after the airpump the tubes going into the buckets are indeed black, about 1m in length from distribution point to airstone.

 

[Toker1]

Might be better for the air line to coil around the OD of the water bottle rather than the ID of the bucket. You can coil it tightly so you don lose any surface area for cooling.

 

[FlyingDutchPaddy]

changed water yesterday.
cleaned system first with H2O2.
cleaned out water tubes (as i've seen with voodoo & sensizym they can get blocked after a while)

pH = 6.4
ppm = 1110

did a small DIY attempt to get water 'circulation' going in the main reservoir... seems to be working as there's much more movement in the water, while still plenty of water going to each plant..
sketch below.

Si - 90ml
CalMag - 30ml
Micro - 30ml
Gro - 15 ml
Bloom - 45ml

a sprinkeling of epsom salts

Voodoo juice - 40ml
Sensizym - 40ml

plants are starting to show pistles

 

[Toker1]

Looking much better today.

 

[FlyingDutchPaddy]

noticed pH had gone up a bit... 6.7

have adjusted down to 6.2 over 1 hour time.

 

[FlyingDutchPaddy]

been a couple of days... Update.

have purchased a 'cooking thermometer'.... does the range... and can use that for the BBQ as well .

pH has been very stable at 6.3 -> 6.1 over 5 days since I added that smaller tube with 3 holes just above the waterpump (see sketch above).
air temp ranging between 17 - 21 C
RH between 45% - 55%

water temperature... measured today at around 19C (66F) - almost the same as air temp.
water has cleared up as well... was a bit 'cloudy / murky' for 2 days but thats cleared up.

plants are looking good & healthy...

getting a but bushy though, so tomorrow at water change i'll give them a mild defoil, get those bud sites back in the light...

 

[FlyingDutchPaddy]

Weekly water change + system cleaning... with pictures of before and after defoil. (and roots of each plant)

week 6 of flower, 18 weeks of life since seed of unknown strain.

thorough clean of entire system with H2O2.
tubes, hoses, waterpump, buckets.
let it recirculate with 30L of water (200ml H2O2 12% to sterilise) for 2 hrs.

plants had a mild defoil.

pH at 6.2
ppm at 1070.
water temp at 18C

air temp 18C
RH 47%

slightly different nutrient mix this time - was reading into optimal NPK ratios.
seems 1-3-2 is a good NPK ratio for early/mid bloom (https://www.zamnesia.com/cannabis-grow-guide/107-npk-ratios)

in a spreadsheet based on the calculation method on https://oaksterdamuniversity.com/combining-n-p-k-ratios/

Micro - 25ml
Bloom - 75ml

to give a NPK ratio of 1 - 3 - 2.6

still 30ml CalMag, 90ml Si+ and 40ml sensizym. (no voodoo juice this time)

probably need a new thread for NPK ratio discussion...