How do you measure

[JMorris271]

PPM? That has got to be a very small spoon. You read about mixing something Xppm. What does that mean?
I know what PPM means but I don't know how to measure that quantity

[Victorg1001]

What are you trying to dose?

[Xavibear]

PPM? That has got to be a very small spoon. You read about mixing something Xppm. What does that mean?
I know what PPM means but I don't know how to measure that quantity

parts per million

It's the unit used to measure different chemicals in the water. It's something measure by testing. When adding things to the tank you be using ml, spoons, cups, etc. Then you will test and your test results will be measured in ppm.

[JMorris271]

parts per million

It's the unit used to measure different chemicals in the water. It's something measure by testing. When adding things to the tank you be using ml, spoons, cups, etc. Then you will test and your test results will be measured in ppm.

So initially it is a guestimate then adjustments to obtain desired results?

[JMorris271]

What are you trying to dose?
Nothing but trying to understand how it works when I do.

[kurt_n]

I think we're just trying to understand the context of the question.

What are you *planning* on dosing? What is it that you're being required to measure in ppm? An actual example would help us help you!

[disc1]

So initially it is a guestimate then adjustments to obtain desired results?

No, it is math. It works out to milligrams per Liter. In reality it should be milligrams per kilogram, but one liter of seawater is close enough to 1 kg (off by 26 grams) that we can just use mg / L.

[disc1]

If you tell me what you are trying to dose and what level you have and what level you want I can help you with the math.

[JMorris271]

I think we're just trying to understand the context of the question.

What are you *planning* on dosing? What is it that you're being required to measure in ppm? An actual example would help us help you!

I am speaking hypothetically. Say I want to add X ppm of something per gal.
How would you know what X ppm. is? I understand something like add 3 tsp. per gal. Bu not ppm.

Thanks David

[disc1]

The problem is that you can't think about it hypothetically. It depends on what you are dosing. In that vein the best I can give you is that ppm is the same as milligrams per liter.

Say for instance you wanted to increase calcium by 20ppm in 10 gallons of water. So you need to add 20 milligrams of calcium for every liter of water. 10 gallons is 38 liters so you'd be adding 760milligrams of calcium to make that change.

If you want to get that calcium from calcium chloride dihydrate which is what most people use for calcium, then you have to figure how much of that is 760 mg of calcium. CaCl2*2H2O weighs 147g/mol. Calcium weighs 40g/mol. So the CaCl2*2H2O is ( 40 / 147 ) == 27.2% calcium by weight. So you'd need ( 760 / 0.272 ) == 2794 mg of CaCl2*2H2O which is the same as saying 2.8 grams.

So all that calculation was to figure out that to raise 10 gallons of water by 20ppm calcium using calcium chloride dihydrate takes 2.8 grams.

If you are one of those people who blew off math class thinking you'd surely never need that, then we have this handy calculator to do it for you.

http://reef.diesyst.com/chemcalc/chem_calc3.html

[JMorris271]

No wonder I couldn't figure it out. It makes sense now though.
And yes,I was one of those students.
Thanks again.

[kurt_n]

Here's another example... using that calculator that David linked to.

When I want to raise calcium in my tank, I add a certain amount of my "calcium cocktail" that I keep on hand. I mix 1 quart of RO/DI water with 4 teaspoons of Kent's Turbo Calcium. That gives me a 7640ppm calcium solution. [Don't ask why I chose that number... it was a long time ago!] You can try it out in that calculator... use 0.25g for tank volume, use 7640ppm for the "desired" level and 1ppm for the "current" level. (The calculator doesn't like 0.0ppm for the start so have to use something non-zero.)

So if I want to raise my tank's calcium level from 420ppm to 430ppm, I just have to figure out the amount of 7640ppm solution to add. I have a 46g tank, that probably contains closer to 40g of water. So I want to increase 40g of 420ppm by 10ppm to end up with 430ppm of 40g water, plus whatever amount of "calcium cocktail" I added.

[math class]

This is where you wish you hadn't slept through Algebra, but you can set up an Excel spreadsheet to solve this for you. You need to solve the following equation for "x" where "x" is the amount of 7640ppm solution you need to add:

[40gallons * 420ppm] + ["x"gallons * 7640ppm] = [40+"x" gallons] * [430ppm]

16800 + 7640x = 17200 + 430x
7210x = 400
x = 0.055

So x=0.055 gallons, and there are 16 cups in a gallon. So I need to add 16*0.055 = 0.88 cups, or about 7/8 cup of my "calcium cocktail" to raise my tank's calcium from 420 to 430.

[/math class]

So if you're looking to increase your tank's concentration of something by XX ppm, there are a bunch of different ways to do it, but you're not really adding or measuring "ppm" of anything directly.