PH Crashing in AG

Hey guys - what an awesome resource!! I've been reading, and started my own AG grow..... it'll be exactly 30 days from seed on Saturday. This is my first (serious) grow ever.

I have 7 plants from bag seed growing in each of the pods, each ranging from about 2" to 4", and bushy. Yes, its mega crowded, but I plan to thin the herd once I determine which ones are Male.

Each week, I siphon out as much water as possible from the tank, and replace it with fresh nute solution PH'ed to 5.8. I only use distilled water, and top off with plain distilled water PH'ed to 5.8 as well. I've got two airstones, use GH Nutes @ 600 PPM, and haven't had a single problem with this grow until the past week.

Anyway, on to my problem:

On Saturday, I put in fresh nute solution, PH'ed to 5.8. Sunday night I checked the PH, and it had dropped to 5.2. So I drained all the water out into a gallon jug, and PH'ed that back up to 5.8 again.

Monday morning I get up, and the PH was back down to 5.0 again. WTF? I drain the water out again, bring PH back to 5.8.

Monday night I check the PH after work, and its down to 4.5!!! WTF? Drain, re-PH back to 5.8.

Tuesday it dropped to 3.9. Wednesday 4.5. Each day, as soon as I can catch it, drain & re-PH.

That's gone on all week. I bring the PH back up to 5.8, and within 12-24 hours, its back below 5.0 again. I don't have a clue what could possibly be causing this, and its starting to take its toll on the plants. What was once lush green, is withering & turning brown.

The *only* thing I can think of that's changed, is I've added an additional fan for more air circ, which blows right on the tank, and has helped keep temps down around 70. (It used to ride around 78 before). But I don't see how that would affect PH.

I removed the extra fan this morning as an experiment - we'll see what the PH is at when I get home tonight. Still, any advice would be much appreciated. I can post some pics later tonight if that'd be helpful!

I ended up emptying & cleaning the tank, and put in fresh nute solution. So far, PH seems to have stabilized, and the plants are already looking a little healthier.


Pics below:

they look a lil droopy, hope they get better

So - this problem seems to be continuing. I'm really stumped on the why... if anyone has an ideas I'd love to hear 'em.

First off - is it normal in an Aerogarden for pH to drop massively in the course of the day? I'm mean 6.5 at 10am, and dropping to 4.5 by 4pm.

Secondly - is it normal for different parts of my 1gallon tank to have wildly different pH? I mean: One section being pH 6.0, and another section (like if I touch my tester near the roots) being 3.75?

What seems to be happening: When I do my weekly water change & put in fresh nutes, pH seems to stabilize for a few days. After that I get back into this pH swing mode. The only thing that fixes it seems to be completely changing out the water.... but every 2-3 days??

There's another, similar thread here that seems to associate this problem with root rot. Save for a few brown spots I attributed to the brown nutes in the tank, my roots look white?!? Someone else mentioned in that same thread that the plant might be drinking nutes faster than the water, making the pH drop. But that doesn't make any sense either.

Pics attached of how everything's doing at the moment, roots & all. I was planning on switching to flower in another week or so, but I'm not sure if its wise to do that before I sort out these pH issues. Feedback appreciated!

never used that ario garden, but i can see you problem...

the plants are using more water than nutes, nutes tend to make the ph fall the more of it you use so if the water drops the salt will rise in consantration making the ph drop.
i think you have to small a water tank to feed that many plants.

try using less nutes and only top off with plain water that should keep your ph about right.

the 4th pic over confermes my thoughts over feed! brown rust spots!

airoponics does not need as much nutes as hydro. here is what to do..

start by lifting the light as high as you can strong light does not help stressed plants!

the feeder tank is to small the water is used up faster than the nutes, so use only half of what you are using > 300ppm.

watch the ph over the next 24 hours if it still drops then cut ppm even more and just use plain water nothing in it no ph up or down plain water only.

you will see the ph settle once you get the ppm correct.

its better to under feed than over feed cannabis is a weed and will grow better with less than to much.

your problem is such a small feeder tank if it was bigger you would not have this problem. airo gardens are for growing small herbs not large fast growin cannabis plants although you can grow them in there you will have a fight on your hands as you are finding out.

p.s
iv seen 5 foot cannabis plants grown in airoponics using less than 500pm and they are thriving!

9inch bigbud said:

the 4th pic over confermes my thoughts over feed! brown rust spots!

airoponics does not need as much nutes as hydro. here is what to do..

start by lifting the light as high as you can strong light does not help stressed plants!

the feeder tank is to small the water is used up faster than the nutes, so use only half of what you are using > 300ppm.

watch the ph over the next 24 hours if it still drops then cut ppm even more and just use plain water nothing in it no ph up or down plain water only.

you will see the ph settle once you get the ppm correct.

its better to under feed than over feed cannabis is a weed and will grow better with less than to much.

your problem is such a small feeder tank if it was bigger you would not have this problem. airo gardens are for growing small herbs not large fast growin cannabis plants although you can grow them in there you will have a fight on your hands as you are finding out.

p.s
iv seen 5 foot cannabis plants grown in airoponics using less than 500pm and they are thriving!

Click to expand...

Thanks for that! I'll give it a try.

The brown spots on those lower leaves you see in that pic started when I let the PH drop below 4 and didn't catch it quick enough. That's also where the tank door lifts open (wrapped in tinfoil) - so those bottom leaves in front get a lot of stress from me opening & closing the tank. I thought about clipping 'em.... but I read somewhere that every single leaf is a sun-collector, regardless of brown spots... so I've left it.

We'll see how it goes... next tank change will be back down to 300ppm.

I know an AG setup isn't ideal, but this is just a personal grow for me - and I'm learning a ton just by dealing with the AG the first time, so its all good

The ph goes up and down in the AG because the rez is so small. Change your nutes according to your nute schedule and top off the rez with fresh distilled water daily as needed. You will have to adjusted the pH to 5.8 once a day. I adjust it every morning. When you change the rez dump all of the old solution out and clean the rez before you put the fresh solution in the rez. You do not have to remove the nutes form the rez to adjust the pH. Just add the pH up or pH down to the rez one drop at a time with a eye dropper until the rez reaches the desired pH of 5.8. This is the nute schedule i use http://www.foxfarmfertilizer.com/hydrofeed.pdf. The ppm's should be adjusted according to your nute schedule and what week of veg or flower you are in. If you look at mine the ppm's start out at 700 ppm's in week one and go up to 1680 ppm's by week 9 of flower. The ppms are determined by the nutrient company's feeding schedule and a little bit of trial and error to see what ppm's work best for the strain you are working with. It is best to start out with the recommended nute schedule from the nute line you are using.