I'm not a chemist, but I play one at home

[dapellegrini]

How does one come to figure out PPM? I know there are some good calculators online for doing the math, but there seems to be something that I am just not catching here and I am really trying to understand what I am doing...

For instance, let's say I am measuring my ferts in grams into ml's of water. If I add 10g of KNO3 to 270,000ml of water (roughly my tank size) then what do I have? 1g per 27,000ml or .000037g/ml, right? Where do I get PPM? do I just multiple x 1,000,000? Would that give me 37ppm?

I am not a complete failure at math, but it has been a few years since I have had to do more than balance my checking account...

TIA

 

[JRagg]

ppm is mg / kg. one L of water is 1 kg, so it's generally accepted for it to be mg/L.

To find out how many ppm of K in that you need to figure out how much of the KNO3 is actually K by using the gram formula weights of the elements. I don't have a periodic table in front of me so I can't do it right now, but it's something like this.

% K = gfw K / gfw (K + N + 3*O)
if that makes sense.

So then you take the amount of mg you added to the tank, divide it by the liters in the tank, and then multiply it by the % that is K (or % that is NO3 if you want to know how many ppm nitrates).

 

[dapellegrini]

That's what those percentages mean... I was trying to reverse engineer the code from Chuck's calculator websites and I saw different percentages being used. In the case of KNO3 I think it was 39%.

So to my example, 10g of KNO3 = 10,000mg * .39 = 3,900mg of K. 3,900mg / 270l = 14.4ppm? (Assuming I got the right percentage)

Or to do it the other way around, 10,000mg / 270l = 37.037ppm of KNO3, of which 39% or 14.4ppm is K. Does that sound right?

 

[JRagg]

Sounds right. Does that give you the same answer as the calculator? I haven't checked any of your numbers.

 

[dapellegrini]

Well wait a minute.... K is potasium, and I need NO3 (nitrate)... That percentage is 61.3.

So 10,000mg of KNO3 give 6,130mg of NO3. 6,130/270l = 22.7ppm.

So 1g of KNO3 will add 2.27ppm of NO3 to my aquarium, right?

If that is right then 1 tsp (5.6g) of KNO3 will add 12.7ppm of NO3 and 8ppm of K in a ~72gal aquarium (270l).

Chuck's calculator uses an interum mixing amount with water and then gives you the outcome of that. I am trying to figure out direct dosing.

What is an ideal NO3 level for a heavily planted tank?

 

[Purrbox]

If you download the windows version of Chuck's calculator it gives you the option of dry dosing directly in the aquarium rather than calculating with a stock solution.

When just starting out, it's generally recommended that you aim for 20ppm of Nitrate in the tank. As you get used to how quickly you tank consumes Nitrates, you'll get a feel for how much you need to dose. After that you can start playing with lower Nitrate levels to try to bring out the reds in your plants while trying to avoid algae.

 

[czcz]

You got it, Dan. Points to consider moving forward:
Accounting for displacement of substrate and other stuff will provide better guesses at fert levels. Many subtract 20-25% from aquariaum volume, and would call your tank more like 240 or 250L.
You will find Gadd and Pituch and others have different mass/tsp conversions for compounds. In your own trials you may find different masses for 1 tsp KNO3 obtained from different sources. Such discrepency is fine for our purposes but calculating by grams is always better (and, as you know, easier).
Fwiw, I dug out my old Chem texts after entering this hobby and find them invaluable. I think other aquarists (re)learning these concepts are well served by picking up some old general Chem book from eBay or the library or something. After a certain point it becomes easier to use the net and BarrReport newsletters and such to tackle the more specific and specialized concepts.

 

[dapellegrini]

What is a good Nitrate Test kit? I have the Seachem one and it is kind of awkward and either I am using it wrong (very possible) or I just cannot achieve any measurable level of Nitrates...

 

[mr funktastic]

u are not showing any nitrates in your tank? that may just mean that your plants are using it faster than your fish are making them. and your tap water may not have any either. the aquarium pharmacuticles kit seems to be the best next to lamott. very easy to read and easy to do. it takes a bit of shaking but it gets the job done lol. my tank alwasy reads zero after a 50% water change and a few days without dosing. my plants use up N really fast.

 

[dapellegrini]

Ya, I just did the Reference check with my Seachem kit and it test out at 10ppm as it should against a 0ppm again from my tank. I am just getting familiar with dosing (obviously) and am alittle surprised at the quantity of NO3 that I need to suppliment. I guess I thought I was adding a lot at a 1/2 tsp per week on top of the PMDD recipe...

I just added 1tsp, which should at least put me back on the map.

Why does Chuck recommend 5ppm of NO3?

 

[mr funktastic]

i was wondering that aswell. the lower the nitrates the more it brings out reds in most plants so that may be why. i think 5 is dangerously low. 15 is a good level to balance at. i add 5 ppm every other day to my tank. it all depends on the type of plants u have. if u have alot of fast growers then u will eat through nitrates really fast. i have alot of moos which just demolishes nitrates. i have a hard time keeping mine above 10 without dosing everyday.

 

[dapellegrini]

I just posted my list of plants and some picks here:

http://www.aquariumadvice.com/viewtopic.php?t=87650

Most I cannot name yet without looking them up on the web...

 

[7Enigma]

If you download the windows version of Chuck's calculator it gives you the option of dry dosing directly in the aquarium rather than calculating with a stock solution.

When just starting out, it's generally recommended that you aim for 20ppm of Nitrate in the tank. As you get used to how quickly you tank consumes Nitrates, you'll get a feel for how much you need to dose. After that you can start playing with lower Nitrate levels to try to bring out the reds in your plants while trying to avoid algae.

Or just put 1ml in for the stock solution volume and you'll get the same results.