Premixing Nutrients - GH Flora Series - Bad pH Drift

[Kazman420]

Hi AFN,

I'm currently working on my first grow and I'm having an issue with really bad pH drift. My plants just entered the flowering phase and are starting to drink a lot more. In an effort to save myself some time I decided to mix up a 5 gallon batch of nutrients. I'm using Heads formula for the flowering phase (modified Lucas formula), along with CalMag since I am growing in Coco/Perlite. Yesterday morning I mixed up my nutes, waited the usual 20 minutes, diluted to the PPM that my girls like, and then proceeded to adjust to 5.8 pH. This was stored in a 5 gallon bucket with a tight fitting lid.

Yesterday evening the nutes had drifted down to 5.5 pH. I corrected it and gave them their evening meal. This morning the pH was at 4.2! What's going on? This can't be normal, can it? Any help would be greatly appreciated!

GH Flora Series (6ml Micro/9ml Bloom per Gallon)
TPS CalMag (2.5ml per Gallon)
Distilled Water

 

[Bruce Campbell]

pH drift in batches of pre-mixed nutrients (or reservoirs) is normal and something that a lot of people experience.

In short, over time, the cations and anions in the mixture eventually neutralize each other and no longer contribute to the overall pH. How fast this occurs and how much pH eventually drifts depends on the specific chemicals and concentrations used in each fertilizer brand (as well as those in any supplements, additives, and impurities in the starting water).

It's why some companies like AN place a lot of marketing focus on pH stability. AN has extra buffering chemicals to slow the drift (but would still drift eventually given enough time), but I've seen a few people complain that GH drift can be more severe than other brands.

 

[Kazman420]

Thanks @KDawg for the awesome explanation! I guess I'll just adjust it each time I'm going to feed the girls.

I only learned about AN's Perfect pH after I had already bought and started with the GH nutes. They are definitely going to be used for my next grow. I'm actually more than willing to switch over to them right now but I've read doing so mid-grow is a bad idea?

 

[Bruce Campbell]

I guess I'll just adjust it each time I'm going to feed the girls.

I only learned about AN's Perfect pH after I had already bought and started with the GH nutes. They are definitely going to be used for my next grow. I'm actually more than willing to switch over to them right now but I've read doing so mid-grow is a bad idea?

I'm not sure what effect the neutralization / drift has on overall plant nutrient availability. If they form weak salts, then they could just have reduced absorption rates but still be available for the plants in the long-term. If they form strong salts, they may effectively become unavailable for plant uptake. Or, there could be no effect at all.

Because of that, I gave up on pre-mixing and just deal with the hassle for now. I wasn't sure if I kept adjusting pH, whether I would ultimately end up with just "pH up/down + unusable nutrients." I haven't checked to see if it would create any issues or not.

As far as AN, I haven't tried them out or compared their stability to other brands - I just know they spend a lot of marketing effort claiming their pH technology is perfect. Technically, there's nothing wrong with changing mid-grow, just that you don't want to create any "I'm not used to this brand" problems mid-grow.

I'd stick with GH and pre-mixing for now. If any issues show up, go back to mixing before each use. And, if GH works well enough for this grow, stick with it for the next grows until you use up what you have (just don't run out mid-grow ).

 

[budwise]

So for your current situation something to think about.

distilled water has very low ph buffering capacity. try out an experiment. mix up your batch using 50 percent tap water and see if it's any more stable. it may not solve the issue completely though as I haven't tried it myself.

I run AN pH perfect as the other poster told you so i don't have this issue.

 

[Mañ'O'Green]

You should have a stirring pump or air stone in mixed nutrients to help prevent some nutrients from falling out of suspension. The PH wander is to be expected. Remember Phosphoric acid PH down or Nitric Acid PH down add phosphorus or Nitrogen respectively to the nutrient balance. If you have to add a lot this can be problematic.

 

[Kazman420]

I'm not sure what effect the neutralization / drift has on overall plant nutrient availability. If they form weak salts, then they could just have reduced absorption rates but still be available for the plants in the long-term. If they form strong salts, they may effectively become unavailable for plant uptake. Or, there could be no effect at all.

Because of that, I gave up on pre-mixing and just deal with the hassle for now. I wasn't sure if I kept adjusting pH, whether I would ultimately end up with just "pH up/down + unusable nutrients." I haven't checked to see if it would create any issues or not.

As far as AN, I haven't tried them out or compared their stability to other brands - I just know they spend a lot of marketing effort claiming their pH technology is perfect. Technically, there's nothing wrong with changing mid-grow, just that you don't want to create any "I'm not used to this brand" problems mid-grow.

I'd stick with GH and pre-mixing for now. If any issues show up, go back to mixing before each use. And, if GH works well enough for this grow, stick with it for the next grows until you use up what you have (just don't run out mid-grow ).

Thanks for the info! Yeah I guess sticking with the nutes I'm already familiar with is probably the best idea. I'm just getting really tired of chasing pH. This morning it had drifted the opposite direction and was hovering at 6.3 pH.

I was kinda planning on trying a DWC for my next grow, which I seriously need to rethink if the GH Flora Series fluctuates this much. (Or just commit to trying it with Advanced Nutrients).

So for your current situation something to think about.

distilled water has very low ph buffering capacity. try out an experiment. mix up your batch using 50 percent tap water and see if it's any more stable. it may not solve the issue completely though as I haven't tried it myself.

I run AN pH perfect as the other poster told you so i don't have this issue.

That's a great idea! Certainly worth a try. I'm assuming that I would need to leave the water out for 24 hours in order to eliminate any chlorine, yes?

You should have a stirring pump or air stone in mixed nutrients to help prevent some nutrients from falling out of suspension. The PH wander is to be expected. Remember Phosphoric acid PH down or Nitric Acid PH down add phosphorus or Nitrogen respectively to the nutrient balance. If you have to add a lot this can be problematic.

I've noticed the nutrient mixture is starting to get a little cloudy. I'm guessing that's nutrient fall out? I'll have to buy an air pump and a stone. (Which is fine since I was planning on trying a DWC next run).

I didn't realize PH Up/Down could do that! I'm using GH's version and yes, it's Phosphoric Acid. I haven't really had to add more than 8 to 10 drops or so. But I can see how it would add up by doing that every time over the course of a few days. Appreciate the info!

 

[tronN00dles]

I pre-mix GH nutes twice a week. I do high-frequency fertigation in coco and I fertigate twice a day. I basically mix up enough solution for 4 days or so.

I use an air stone as well, but I still have to pH adjust every time I fertigate. This is totally normal, and has just become part of my routine.

Happy growing

 

[Kazman420]

I pre-mix GH nutes twice a week. I do high-frequency fertigation in coco and I fertigate twice a day. I basically mix up enough solution for 4 days or so.

I use an air stone as well, but I still have to pH adjust every time I fertigate. This is totally normal, and has just become part of my routine.

Happy growing

Thanks for the reply tronN00dles! It's good to know I'm not the only one experiencing this problem. Now I see why everybody complains about chasing pH..

Not sure if anybody reading this has done a DWC, but how is it even possible with nutes that drift so much? Wouldn't it cause all kinds of problems/stress/lockouts for the plant? Is the only way to do it with Advanced Nutrients brand? Or do you just have to keep up on it constantly?

 

[tronN00dles]

Thanks for the reply tronN00dles! It's good to know I'm not the only one experiencing this problem. Now I see why everybody complains about chasing pH..

Not sure if anybody reading this has done a DWC, but how is it even possible with nutes that drift so much? Wouldn't it cause all kinds of problems/stress/lockouts for the plant? Is the only way to do it with Advanced Nutrients brand? Or do you just have to keep up on it constantly?

I can’t comment on DWC, but I think it’s less about aiming for a target pH, but rather a target range. You hear about 5.8-6.2 for coco for example. I always aim for 5.8, because I figure by the time I fertigate again, it will have drifted back up to 6.2. But I always stay in that range, so I’m happy.