How do you arrive at ppm's? - The Planted Tank Forum
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post #1 of 18 (permalink) Old 05-07-2005, 07:03 PM Thread Starter
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How do you arrive at ppm's?

How do you do that?
I simply use Wolfy's chart (what a Godsend) for dosing ferts. With this, I know to add žtsp, (75G tank) for instance, of Phosphates.
I have no idea what ppm's this comes to.
Would someone please speak slowly and carefully, and show me how to arrive at ppm's?
Thank you.

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post #2 of 18 (permalink) Old 05-07-2005, 10:17 PM
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Well you can use a test kit as most of them give readings in ppm. Or you can use Chuck Gadd's Calculator http://www.csd.net/~cgadd/aqua/art_plant_aquacalc.htm to figure out your dosing and it will tell you how many ppm you get for a given dose.


If you are dosing KH2PO4 (Mono Potassium Phosphate) in your 75 gallon tank you are dosing right at 3 ppm with every ž teaspoon.
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post #3 of 18 (permalink) Old 05-08-2005, 04:32 AM Thread Starter
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Looking at Chuck Gadd's calculator, if target level of Potassium(K2S04) is 20ppm, would I actually need to dry dose around 2 tsp to achieve this? MAN, that sounds like an awful lot.
I have only been dosing žtsp.

Am I understanding correctly, or do I have it all flubbed up?

Thank you for your patience.

...oh and if 2 tsp is the correct dosage, do I add 2 tsp per 75 gallons every other day? Or would that cause some kind of buildup?
Does the calculator consider that the 75 gallon tank is brand new with no Potassium yet added?
How do I know how much has been used up every other day?

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Last edited by Barbels; 05-08-2005 at 05:13 AM. Reason: ...oh, and...
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post #4 of 18 (permalink) Old 05-08-2005, 05:55 AM
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Make sure that you change the amount of water when punching in the numbers. Otherwise, that's the amount you should be adding to water instead of dry dosing.

Taking into consideration of the size of that tank, you're in the neighborhood at 1/4 tsp. Really depends on what kind of plant mass you're dealing with here, but it won't be anywhere in the neighborhood of 2 tsp. every couple of days. I'd stick with 1/4 tsp. phosphates, for that size tank, and if you're noticing deficiency, then increase it up to 1/2 tsp.

If you're going off the Estimative Index (EI), and according to Craig's chart, that'll be 1/4 tsp. every other day. There's also a weekly water change (on the 7th day) and this is what takes care of the buildup. You really won't be able to tell how much your plants are using on a daily basis, unless you are testing each day with very precise test kits (you'll have to continuous do this since the increase in plant mass will alter this, and when you trim, this will change also). That's the beauty of EI; it allows you to grow plants without the need to constantly be measuring the levels.

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post #5 of 18 (permalink) Old 05-08-2005, 06:26 AM
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Quote:
Originally Posted by Barbels
Looking at Chuck Gadd's calculator, if target level of Potassium(K2S04) is 20ppm, would I actually need to dry dose around 2 tsp to achieve this? MAN, that sounds like an awful lot.
I have only been dosing žtsp.

Does the calculator consider that the 75 gallon tank is brand new with no Potassium yet added?
How do I know how much has been used up every other day?
Yes, you have it right here. If you have never dosed for the K(K2SO4), then just the first time add the 2 teaspoons. But bear in mind if you are dosing KNO3 and KH2PO4, there is a lot of potassium in those ferts. Some don't dose potassium sulfate, because they are dosing so much K with the phosphate (KH2PO4) and Nitrate (KNO3).

But after the first change, just dose to the new amount of water added to the tank, I believe. Somebody correct me if I'm wrong. For example, dose for 30 gallons (~.75 teaspoon) if thats all you are changing. Usually, when in doubt I underdose on potassium, but I don't think it is an algae issue. More of a calcium uptake issue if too much potassium. HTH bob





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post #6 of 18 (permalink) Old 05-08-2005, 09:37 AM
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You don't need to dose the full 20ppm every other day. I would dose about 3/4-1 tsp K2SO4 every other day. If you also dose KNO3, then you can reduce K2SO4. K from KH2PO4 is not much, can be ignored.


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post #7 of 18 (permalink) Old 05-08-2005, 03:16 PM
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edit - corrected my error

ppm (part per million) = mg/l (milligrams per liter)

cc (cubic centimeter) = ml (milliliter)

There's 3.785412 liters in 1 gallon.

Measuring by weight (using a scale) is usually more accurate than measuring by volume (using a measuring spoon)

Last edited by Hypancistrus; 05-13-2005 at 10:09 PM.
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post #8 of 18 (permalink) Old 05-09-2005, 04:59 PM
 
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Quote:
Originally Posted by Hypancistrus
ppm (part per million) = cc (cubic centimeter) = mg/l (milligrams per liter)

There's 3.785412 liters in 1 gallon.

Measuring by weight (using a scale) is usually more accurate than measuring by volume (using a measuring spoon)
very true. then again, we're growing aquatic weeds...not doing rocket science. If you don't have a dry scale, measuring spoons work just fine. a heaping teaspoon is about 5g, a level teaspoon is about 3g.
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post #9 of 18 (permalink) Old 05-09-2005, 11:45 PM
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Quote:
Originally Posted by Hypancistrus
ppm (part per million) = cc (cubic centimeter) = mg/l (milligrams per liter)
ppm=mg/l is correct for water solutions, which is our case, because 1litre water weighs 1000grams=1million mg. but cc is volume, = ml(milli litre), totally different unit.


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post #10 of 18 (permalink) Old 05-11-2005, 10:41 PM
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A level 1/4 teaspoon is accurate to about 1 ppm of NO3 for KNO3 dosing.

I do not know of any test kit that is accurate to 1ppm NO3 that is sold in the hobby.

There are other devices that are accurate to about 0.01ppm NO3 of so and less expensive ones at 0.1ppm.

If you need that precision, you likely will have no issues dosing with a dosing pump because you simply cannot maintain a stable NO3 level (except in rare cases were fish load add enough in low light CO2/non CO2 tanks etc) with a measured consistent range of say 10-12ppm and keep and maintain it there without daily precise dosing.

Knowing the rate of uptake is more useful.
Knowing that all tanks are different in this uptake rate, assuming the highest uptake rate, which would be at high light/CO2 and non limiting nutrients would be a safe assumption.

Then all the nutrients would be supplied to any tank no matter what the tank.
You can guess the rate of uptake for lower lighting, non CO2 methoid etc as well.


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post #11 of 18 (permalink) Old 05-13-2005, 01:50 AM
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thread hijaking about to happen...maybe

Quote:
Originally Posted by shalu
ppm=mg/l is correct for water solutions, which is our case, because 1litre water weighs 1000grams=1million mg. but cc is volume, = ml(milli litre), totally different unit.
so...if i have a syringe that measures in cc and i want to measure wet solution (pre-mixed by a friend using chuck gadd and greg watson) of say KNO3 can i use it or should i get a different syringe? i killed my tank with EI and perhaps this is why.

thanks!

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post #12 of 18 (permalink) Old 05-13-2005, 02:13 AM
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edit - shalu was correcting my error

1 CC = 1 mL

Last edited by Hypancistrus; 05-13-2005 at 10:10 PM.
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post #13 of 18 (permalink) Old 05-13-2005, 02:15 AM
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Now I'm just a stupid American that doesn't use the Metric system and it has been many years since I took high school physics and chemistry. But I seem to recall that a ml and a cc of water were the same thing.

1000 cc to the liter and 1000 ml to the liter.
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post #14 of 18 (permalink) Old 05-13-2005, 02:17 AM
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I'm not sure what you're asking Kris.

1 mL = 1 cc

Here's an example using arbitrary numbers. Maybe it will help you.

Say you dissolve 50 grams of KNO3 in 250 mL water. You will then have a stock solution containing 0.2 g/mL, which equals 200 mg/mL.

Now say you want to add 10 mL of this solution to 100 litres of water. What will your ppm be?

Well, 10 mL of the stock solution contains 2 g.

Add 2 g to 100 litres. This is the same as saying you are adding 2000 mg to 100 L. So divide 2000 mg by 100 L and you get 20 mg/L = 20 ppm.

Of course, one of the variables involved with dosing dry powders is density. 1 mL water, if memory serves me correctly, weighs 1 g. But most solids are more dense than water and of course have differing densities, so you can not reliably say that 5 mL (or 5 cc) of KNO3 powder will weigh 5 g. In fact, you can be sure that it does not!

Kris hopefully that will help you.

EDIT: Looks like a few of us replied at the same time! Hopefully my post is not too redundant!
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post #15 of 18 (permalink) Old 05-13-2005, 03:54 AM
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thanks everyone!
that does help clear some things up.
i didn't realize that mixing the solution converted from mg to ml.
jart your answer was quite clear and good.

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