pH Balancing for Hydroponics

[javagamer]

Hello,

I'm growing some plants hydroponically and I've realized the pH is tending towards basic, while it should be in the 5.5-6.0 range. I'm wondering how I could best move it there with easily attainable chemicals, and it keep there. My previous method consisted of mostly adding in a splash of pH down solution (which I believe is just sulphuric acid) we have sitting around, then adding a splash of baking soda when I end up overshooting my target pH (I have at most 5 gallons of water in my hydroponics system so overshooting isn't very hard).

 

Obviously, this isn't a very good method since it's very error-prone and I'm running out of pH down. My first question is: What could I use for pH up and down? For pH up I think baking soda is probably the best choice since it's certainly available, cheap, and as far as I know not very harmful to my plant. For pH down I'm more unsure. I have HCl, but it's from a hardware store so I have no idea how harmful the impurities might be. I also have hardware store sulphuric acid which is obviously very impure, but I might be able to clean it with some activated carbon. I also have some technical grade sulphuric acid from Fisher Scientific, but I'd rather no use that since it's more limited.

 

My second question is more math involved. Once I have a pH down how much would I need to add to get the pH in my target range? I'll be replacing the water with distilled water soon, so we can assume a pH of 7.0 . Now, I probably won't have it filled completely with 5 gallons, but I think assuming it is 5 gallons and then that I want a pH of 6.0 will probably work. So once I have an acid how do I determine how much I need to add to bring the pH of 5 gallons of distilled water to a pH of 6.0?

 

My final question is: How do I keep the pH in this range? I don't know a whole lot about buffer solutions, but I have a feeling they could be useful. I also read on wikipedia that the pH of carbonic acid in equilibrium is between 5.5-6.0 so would there be any way to constantly bubble CO2 through it to keep the pH down? I'm using a DWC system so air is already being bubbled through.

 

Any help is appreciated!

[hermanntrude]

the most easily available acid is probably acetic, but i don't know what the acetate ion might do to your plants. After that, hydrochloric might work, since chloride ions are everywhere anyway....

[javagamer]

I think the chloride ion is actually harmful now that I think about it. IIRC it sucks water out of the plant through diffusion, though I guess most ions would do that, right? Also, might household strength vinegar be good enough? I don't have any GAA yet.

[John Cuthber]

Given what salt does to plants I'd give HCl a miss.

IIRC Ammonium sulphate will reduce the pH and supply nitrogen but ,as with all things, you don't want to overdo it.

I sugest that you take a known amount, say a litre, of water from your system. Add the acid to that and measure how much it takes to get to the right pH then you can work out how much it will need to sort out the pH of the whole lot. (if it's 5 gallons then it takes 21 times as much acid to get the pH of the bulk of the solution to a given pH as it takes to get 1 litre to the right pH). Add most of that much acid and mix it in and see how close to the right pH you are.

It's possible to get to the right pH by overshooting with the acid then adding a base but you don't want to add any more stuff than you need.

[javagamer]

Yeah, I know, everytime I overshoot and add base I end up creating more salts in there which my plants can't enjoy. I was hoping there was some mathematical formula I could use to find how much of an acid I would need to add rather than through experimentation since I don't have a very good means of measuring pH. All I have is a pH meter which appears to work to .1 of a pH, though it moves around a lot before it settles on a value. Also, ammonium sulphate sounds like a good idea, thanks.

[gcol]

The "standard" ph adjuster used by hydroponics afficianados is phosphoric acid. I thought this was well-known, but as it has not been yet mentioned.....

 

It is food friendly (coca cola is dosed with the stuff).

 

It is available from any good hydroponics equipment supplier online (Including everything you need for growing various medicinal "weeds"). They also have what you need for measuring ph and instructions as to practical methods for adjusting it as required.

 

If you have any left over, use it to rustproof your iron and steel tools, clean copper. etc.

[greenprogrammin]

I too am a hydro grower.

 

I try not to use pH up or down. If you use General Hydroponic 3 part nutrient it will adjust your pH to about 6 for you. Your ppm and pH will be just about right for the application (seedling, veg, transition, bloom).

 

I'm trying to figure out a good buffer for the system also. I'm thinking Dipotassium Phosphate and Monopotassium Phosphate. I have to analyze this and see how it works in application. If you keep this thread alive I will report my findings.

 

 

The pH scale math formulas are all logarithmic from what I understand. What nutes are you using? What strain? hehe... I'm running Auto Flowering strains of Hindu Kush and Diesel Ryder. If you get into the gentics let me know!!! I'm building databases of inheritance patterns as I collect data. Soon I'll be adding two more auto strains and following non auto and auto hybrid patterns.

Edited January 28, 2010 by greenprogrammin

[Christopher Walken]

Thanks for posting such a good information

 

 

 

 

 

I have gotten a lot of help from this forum related to hydroponic tips and ideas. I thought I would share this. Not sure how long this link helpful for you.

 

 

 

 

http://www.rosebudmag.com/hydroponic-tips-ideas