Backyard Aquaponics
A place to discuss aquaponics

Someone teach me how PH works, ie if I have a ph of 9 and want it to a PH of 7, can I add lower PH water to achieve this, and how much? My brain can't get around it not being simple math. Any help?

In simple terms, this will work. It's logarithmic as steve was saying, so if you have 1000 litres at ph 9 and put in 1000 litres at ph 7, it won't make ph 8. But as for the math, beats the hell out of me!

HUH ...
Yeah! well, I dont quite follow the math of that either.... (so what will you get then?)

All I know are some factors which will swing a PH down, and some ways of swinging it back up again. I try keep my ph around 7 to 7.5ish...

I dunno what you would get, a headache maybe from trying to work it out? I know that when my ph was 7, i added 600 grams of marine aquarium salt and it buffered it back to 7.4 plus it is helping to keep it up there ( Isuppose the true meaning of buffer )

true!
I have to look into the buffering side of things better!

GF, in addition to the log scale there is the buffering thing which has been mentioned. You can add water of a lower PH to bring the PH down, but i can not tell you how much becasue even if i knew how to work it out it depends on the alkalinity ( buffering capacity) of the original water. You could also use an acid (lemon juice if you want ) to bring it down.

SLOWLY is the KEY. Fsih don't like rapid changes of anything. 0.2 per day has been quoted on some sites, and definatly not more than 0.5 per day.

The easiest way i think to get the "amounts" you need is to take a known quantity of water, say 10L and add one teaspoon at a time of acid, or "ph lower" buffer, or lemon juice. Measure ph change after each teaspoon until you get the change you want.

So, if it takes 2 teaspoons of lemon juice to bring your water from PH 9 to PH 8.5 in a volume of 10L, and your tank is 100L then you now know that you will need 20 teaspoons to bring the 100L from ph 9 to PH 8.5. Make sense?

Also, if you use a "ph lower" buffer use MUCH LESS than a teaspoon (per 10L) to start with, Up and DOWN buffers have huge.........well..... buffering capability!

Steve

I'm not really concerned about buffering at this point just if I had a gallon of ph 6 water and a gallon of ph 8 water , when I mix them I would have 2 gallons of water at a PH of 7 correct?
so it follows from the table DD posted
0 14
1 13
2 12
3 11
4 10
5 9
6 8
7 7
All of those combinations of ph when combined in equal amounts will give you a ph of 7.
And the formula. When adding equal amounts holds true.
.50x + .50y = z
where x equals one ph
where y equals another ph
where z is thier combined ph
Any help in this? Did I miss something?

GF,I think what is being pointed out is that the PH may be around 6.5 instead of 7 and the calculation isn't as simple as 1+1=2, by using a gallon bucket of water and adding PH up/down in small measured doses a reasonably accurate measure can be obtained to change the PH by a desired amount - and only make small daily PH changes

Les

Understand Ell and I totally agree with the small Ph changes, or small changes in any area to any stable system for that mater.
But could you answer my previous post?

Never mind I surrender.

LOL I am useless to you!

GF, LOL

The point IS "buffers" both your tank water and your town water will have buffers in it, making it impossible in the real world to answer your post.

Which is why i posted the little proceedure using a small volume of water!

True communication is difficult to say the least.
But we battle on.
Steve are you in agreement that (discounting any buffering capacity) one can mix a cup of 6ph water and a cup of 8ph water with the result being two cups of 7ph water? Please explain why you agree or disagree?

GF, i a big fan of having the humility to admit when you don't know something (versus baffling with bulshit).

I don't know.

BUT if i had to bet on it i'd say that you're on the money.

if you wanted to test your theory out emperically then use an acid like hydrochloric acid to dose sample one to ph 6 and something like sodium hydroxide to dose sample two to ph 8.

Let us know

Wish that I had the available test devices and chemicals to do that. Alas I just use the pool strips with the color changing tabs for my testing and they won't give anything but the (yep your close reading).
I do now understand what you ment by the buffering though, with its resisting ph change one would be unable to easily calulate the resulting Ph of a mix.
Sometimes my brain needs to marinate in its thought process before it soaks in.