Fighting with a lowering ph

Hi guys!

I live in a small Italian town and it is difficult for me to get nutes specifically design for hydroponics or Mary Jane (seems the only ones using hydroponics nutes here are those involved in cannabis cultivation...;-). I was able to get the GHE tripack stuff and I used it for quite some time with nice results.

I run a very small DWC setup, 6 small buckets (4-5 liters each) under a small 150 watt HPS, that provides me with enough weed to enjoy myself.

Recently I decided to use nutes I can find downtown without looking too suspicious: it is a soluble fertilizer from the German Manna, called MannaLin. I'm using the A and the B versions (20-20-20-4Mg the first, 8-12-24-4Mg the second, plus micro).

Since I use reverse osmosis (RO) water I also add some more Mg, some calcium and some sulfur, using calcium nitrate, calcium chloride and epson salt.
If I did my home work correctly I should get this profile:
N 102,5
P 36,12
K 139,44
Ca 80
Mg 44
S 34
This quantities may vary a bit, but not too much. Concentration is not very high for flowering: I usually start at 500 uS (microSiemens - "u" stands for mu) and get to around 800 uS (from 250 to 400 ppm with a 0.5 conversion factor).

Now, my nutes come without any ph buffer in it, and here comes the problem: when I prepare the solution I get a ph of 5.8-6.0. After a couple of days, it depends on how much the plants are eating, the ph drops in the 3.3-4.0 area.
To rise it I tried using potassium bicarbonate, calcium carbonate, a mix of potassium and sodium bicarbonate (to increase alkalinity). After a couple of days the ph comes back in the 3.3-4.0 area.... I've also tried mixing tap water to my RO water, without result.

Unfortunately I cannot use tap water: even by adding a lot of acid (nitric or phosphoric acid) I cannot get the ph below the 7.5-8.0 area.

If I constantly keep an eye on my plants they seem not to be suffering too much from ph fluctuations: no deficiency shows up, roots are fine, and so on. But I would like to have a more stable situation so I can leave them for 2-4 days without having to adjust the ph constantly. I would like to avoid hydroponic specific nutrients, very difficult to find where I live. I know that with GHE stuff I do not have these problems, but I would like to be able to prepare a ph buffer that is suitable for my needs.
Is there someone that can help me? That would be greatly appreciated.

have fun and stay safe.

Why not

Why not

Try ordering online? PH Up/down should be easy to find.

atlantishydroponics.com

gattorama - buddy, while PH is important, don't loose too much sleep over it if your plants are doing fine. If you can keep it between 5.0 & 7.5 thats all you have to care about with your type set-up. I know alot of growers will dissagree, but the plants will tell you what they need. My set-up is identical to yours. 6 tubs, each 4 litres, under a 150HPS. I've been growing this way for years with great results, and I stopped checking my PH several years ago. Of course, I do grow exclusively with rain-water. Check out my Grow Thread by following the link in my signature. You may find a couple of good tips or ideas. While you're there, drop a post if you see something you like or hate.

Pipedream

Hi Pipedream,
thanks for stopping by!

Yes, indeed, my setup is very similar to yours... actually you were my inspiration, and I think I dropped a couple of messages during the overgrown times. So this is a good opportunity to thank you once again for sharing your interesting and very useful experience.
I also asked this question in the 150 club, but probably this is too hydroponics specific...

Now, if I use nutes designed for hydroponic use (such as GHE Flora series) I do not have any problem with ph and related deficiencies.

Still, I'd like to be able to prepare my nutes starting with fertilizers you may find in general purpose gardening shops, with the "do it yourself" philosophy I'm sure you understand.

In other words, when I start using nutes without proper ph buffering capacity I'm getting ph fluctuations that bring nutrients' lockups and thus many deficiencies.
Since I'm far from being a water chemistry expert I hoped that the community could have enough knowledge to provide a working recipe.
I've spent some time in surfing the web, but I could not find any way to fight against the natural nutrient solution acidification process.
I'd like to experiment with some buffer solutions I have in mind (dibasic and monobasic potassium phosphate in the proper ratio, MES, and so on) but it seems quite hard to find those needed chemicals.

So, for the time being I'm using the General Hydroponics Europe Flora series without problems, but if someone can help in providing the recipe of a home made nutrient solution (or at least a home made buffering solution), well, this would be great!

Thanks superpedro for your link. I must confess I'm a bit paranoid though. Did you read this stuff:
http://legale.antiproibizionisti.it/videosorveglianza-su-un-growshop/
(a grow shop under video surveillance by the police).
Safety is my major concern and I keep reading that LEOs in Italy seem to start using investigation techniques I've heard are being used in the US. I hoped the new administration was going to abolish the latest Berlusconi's drug legislation, instead it seems that Berlusconi could be our next prime minister, with that very law still in force (now in Italy growing mary jane is a major felony, and consumption of ganja is punished in the very same way of heroin consumption!). This is scary!

Thank you guys for your kind attention.

pH fluxing down - you are over feeding. Do partial swap-outs with pure water until pH stabilizes at the point you require. If your tap water has low pH (uncommon), you'll have to add pH up to help stabalize the pH.

ReeferCat said:

pH fluxing down - you are over feeding. Do partial swap-outs with pure water until pH stabilizes at the point you require. If your tap water has low pH (uncommon), you'll have to add pH up to help stabalize the pH.

Click to expand...

Hi ReeferCat!
I'm far from overfeeding them, that's for sure! And I'm not using tap water, but RO water. This is where my problem comes from, sort of...

I suffer of a ph drop only when using home made nutes: nutes I did myself by blending general gardening fertilizers and some other needed chemicals.
When i use commercial fertilizers designed for hydroponic uses, such as the GH Flora series, I do not have this kind of problem.

In other words, what I'm trying to do is to reproduce the buffering capacity of commercial hydroponic fertilizers. The problem is that their recipe is a trade secret. Moreover, in the case of GH Flora series, they talk about some mysterious organic buffers:
http://www.eurohydro.com/floraseries.php?lang=gb

But if you look in the component list, nothing shows up:
http://www.eurohydro.com/pdf/security/gb/flora_gro.pdf
http://www.eurohydro.com/pdf/security/gb/flora_micro.pdf
http://www.eurohydro.com/pdf/security/gb/flora_bloom.pdf

Thanks for your kind attention.

how fast is your water levels dropping? if they are using water faster than they are using nutes (which they will) and you don't add more, the nutrient concentration will rise, lowering the pH.

Ok, I solved my problem, and wanted to report back with the hope that this information can be useful for someone appropriately using the search function of this forum.
The problem I was facing was due to the high levels of ammonia in commercial fertilizers. Since those fertilizes are not used for hydroponics, let alone DWC, but are intended for soil, usually the majority of nitrogen is ammoniacal, with a smaller part as nitrate. This formulation in DWC leads to ph drops over time.

If you look at the formula of General Hydroponics Flora series, you'll see that in flowering (or with the Lucas formula) only 0,3% of total nitrogen is ammoniacal:
http://www.angelfire.com/cantina/fourtwenty/articles/nuteoramapremixppm.txt

So, with the help of sproutco, who is not a member of our community anymore since he got banned, and others who animated the thread linked below, I prepared my own nutrient solution, with nitrogen as nitrate only (I'm also testing a formula with the 11% of nitrogen as ammonia for the vegetative growth), just using monopotassium phosphate, potassium nitrate, calcium nitrate, magnesium sulfate, ammonium nitrate together with some commercial micro elements.
More info can be found here:
http://www.icmag.com/ic/showthread.php?t=51091

Thanks for your kind attention.