Rising pH in coco drip system using citric acid

[copperrein]

Hello coco comrades! Sweet jesus someone throw me a brain wave because I'm at the stage where panic overtakes cool logic:

I have crafted a very neat tiny 3-bucket drip system. Think Red Green meets Ricky and Julian growing in a 2x4.

The whole point of this system is so I can run coco-perlite and have the watering automated because this summer is going to be stupid-busy. The journal is here.

Here's a copy and paste of my question:

My pH isn't stabilizing. I was trying to use citric acid as a pH down, thinking no phosphorous might be better but alas I'm starting to wonder if not all acids are created equal?

I've put about 50g of citric acid into my system (now sitting at 14+gallons thanks to diluting the acid prior to adding into the system) and the pH will go down and stay stabile for two or three cycles of my system (1.5 to 2.25 hours) and then start rising again. Yesterday afternoon I adjusted the pH down to 5.5 and by 10p it was back up around 6.5.

Adjusted back down to 6 before going to bed. It was at 7 this morning. I like micromanaging my grows but this is a little nutzo.

Is this just coco? I rinsed my media incredibly well multiple times. If this is coco I can rinse my babies and just go perlite. Is it perlite? There's another new variable. Dammit.

I've also found some vague hints on other forums that citric acid isn't the most stable of acids. Doesn't an acid just come into a system, rip or forcefully give ions until depleted, and then the solution is just sitting at that pH if the system it's in has no other inputs/withdrawals?

How are there no chemistry teachers on here? I'm pretty damn sure my high school chem teacher was smoking the weed my ceramics instructor grew.

Once I'm functional I may flush the entire system and start over with phosphoric acid just so I'm not working with multiple variables while trying to troubleshoot this.

So yeah, I bought good coco and rinsed it out in a fine mesh bag until the water was clear. I put the coco/perlite mix into the system without nutes for 2 days prior to planting my girls and let it run at 3 seconds every ten minutes. Now since the sprouts are in it I've dialed back the frequency of sprays to 3 seconds every 45 minutes.

 

[Rider509]

Better living through chemistry? LOL. Don’t know about citric acid but your logic is sound. There’s another grower here that’s experiencing the same dilemma. pH will start at 5.6 and raise to 7ish in a day. Gimme a sec to dig through and find the discussion in his journal.

 

[Weaselcracker]

The amount of phosphoric acid used is really small and shouldn’t affect anything much anyway. It’s pretty much the industry standard. Sulphuric acid is also a good option and you can get it from an auto supply- but have to put a bit of work into diluting it.

 

[Rider509]

My thoughts:
Citric is way too weak and peters out quickly. I’d use a phosphoric based product. Or use a nitric for veg and phosphoric for flower.

 

[copperrein]

Thanks @Weaselcracker And @Rider509

I changed back to phosphoric last night and my pH is much more stable. It sounds like I have a little more wiggle room with coco, right? The kind I have is pre buffered to stay at the 6.3 to 6.8 range

 

[Weaselcracker]

That sounds weird. That’s kind of outside my coco experience. If it is buffered with lime like soilless, then you probably do not need to pH adjust your feeding- because it’s buffered. But all the coco I am familiar with growing in is not buffered. What’s the brand name?

 

[copperrein]

That sounds weird. That’s kind of outside my coco experience. If it is buffered with lime like soilless, then you probably do not need to pH adjust your feeding- because it’s buffered. But all the coco I am familiar with growing in is not buffered. What’s the brand name?

Envelor. I was reading through posts here and I think in Greg Green's book he mentions that there's several types of coco coir processing methods. There's inner pith and outer fibers and some contain more calcium (if I recall correctly) and one of them holds onto more oxygen. Companies tweak the percentages of those and then do all sorts of weird shit to it, mostly for pH reasons.

Rambling, sorry. Anyhoo yeah... The stuff I have is tweaked. I didn't know it was a thing when I bought it so it is what it is.

Edit: what do you mean by 'buffered with lime like soiless' ?

 

[Weaselcracker]

You made it sound from your previous post like it is pH buffered. Normally that’s done with dolomite lime or some other variations of lime.

Peat/perlite mixes like Promix and Sunshine mix use lime as a PH buffer. With that lime present to act as a buffer, there is no need to adjust the ph of the nutrient solutions we add.

Normally coco is unbuffered and coco growers need to adjust their PH to the hydro range of -around 5.8.

I have no idea what the deal is with your coco or how to approach it. Would be best to ask the manufacture.

 

[copperrein]

You made it sound from your previous post like it is pH buffered. Normally that’s done with dolomite lime or some other variations of lime.

Peat/perlite mixes like Promix and Sunshine mix use lime as a PH buffer. With that lime present to act as a buffer, there is no need to adjust the ph of the nutrient solutions we add.

Normally coco is unbuffered and coco growers need to adjust their PH to the hydro range of -around 5.8.

I have no idea what the deal is with your coco or how to approach it. Would be best to ask the manufacture.

Ohhhh! Gotcha!

I did avoid promix since it had a lot of reviews saying it runs hot for a soiless. Lemme wake up and I'll send you the manufacturers page privately. I may not be understanding something.