Help with KNO3 dosing amounts...please

[CELACANTHr]

Ok, my tank is 37 gallons. With sand and rock it is roughly 30 gallons (probably more, but better to underdose than overdose).
30 gallons=114 (rounded) liters
114 liters=114000 mL
1 ppm of 114000mL=.114 mL

so to raise my nitrate to 5ppm I would need to add .5 mL (roughly)
to raise it by one ppm I would need to add .114 mL

Please please please check my math! Thank you.

Now I need to figure out how I am gonna dose this. Suggestions?

Thanks,
Roo

P.S. I am gonna use spectracide (sp?) stump remover for the KNO3, since none of the stores has greenlight stump remover.Spectracide's MSDS says it is 100% MSDS.

[Samala]

Roo dearest, we've gone a bit off track.

We need to know the concentration of your KNO3 solution in order to get a dose amount for your tank. I could make several different concentrated solutions of KNO3 (say 1M or 3.5M or 8M) and each of these would have different dosages needed to hit your target ppm level. The more concentrated the solution, typically the less you need of it to reach your target.

So, you've got roughly 114 liters of water. In aqueous solutions 1ppm = 1 mg/L. You want a target level of 5ppm, or rather, to raise the overall tank by 5 mg/L. 114L multiplied by 5 mg/L tells us you need to add (in each dose of solution) 570mg.

[You can make a 'dose' equal to practically anything, but I find it easiest to make it equal to 1mL.. mostly because I have pipets that are marked in ml increments.]

Now.. about 61% of the weight of KNO3 is the actual nitrate part. So we need to add enough KNO3 that 61% of the total dose = 570mg. About 935 mg total, or very nearly 1g.

How do we use this information? Well, lets say you make up a 1Molar solution of KNO3 - 101g / L of water. That's equivalent to 101 mg/ml. So for each ml of solution you're adding 61mg NO3. 61mg in 114L yields 0.54ppm NO3. About one tenth of what you're aiming for. With this solution you would need to add 9.3 ml of KNO3 solution.

This may actually be ideal if you tend to be a bit clumsy (like me!) and are afraid to work with more concentrated stuff, or are okay with dosing in ~10ml of solution each day. As I mentioned you can make a dose very small (1ml) or larger, whatever way is best for you. More dilute solutions can be great if you are dripping in the KNO3 throughout the day.

How do you make a 1M KNO3 solution? Well, you need something fairly reliable for measuring 1liter's worth of water. Then you need to add 101g of KNO3 to it, and stir well. A teaspoon is roughly 5.5g, so mix in 18 tsp's worth. You could then add about one and a half tsp's of your KNO3 solution each day to the tank.

Now that you have a stock solution of 1M KNO3, you can add any amount of nitrate to a tank of any volume fairly reliably. Just know that each 1ml of your solution = 61mg NO3.

For ex. if your tank was instead a 50gallon, and your target level was 1ppm NO3:

50 gallons --> 189 L
1ppm = 189 mg/L needed
189mg / 61mg per ml = ~6ml needed of stock solution

Chuck Gadd's calculator is marvelously handy for these kind of calculations if you arent inclined to scratch them out yourself. They work the same for salt as they do for freshwater: Chuck Gadd's Dosing Calculators.

>Sarah

[CELACANTHr]

Wow, that made my head hurt.
So why are we using a measurement of weight, when we are talking about volume?

[Samala]

Rats Cela! I wish I was better at explaining this stuff, then maybe everyone wouldn't need to rush for the Advil bottle after listening to me blabber on.

I think you mean mg/L as the 'measurement of weight'?

In solution where H20 is the major solvent (the majority of the solution) ppm is the same as saying mg/L. "Most water quality measurements are recorded in milligrams per liter (mg/L), or the number of milligrams of a contaminant that are present in one liter of water. One milligram per liter (mg/l) is equal to one part per million (ppm) because one liter of water weighs 1000 grams and one milligram is one one-thousandth of a gram. Therefore, there are 1,000,000 milligrams in one liter of water, and each of those milligrams equals one part per million." (Chopped that from my textbook.)

Make sense now? So basically you have a target mg/L or ppm level you want to attain and you know how much water you want to raise by that ppm level. All you need to know is how many milligrams (mg) you need to do it. You could measure out those milligrams on a scale and dump in the KNO3 dry to the tank, but that's a hassle and these are very small amounts. Its easier to make a big solution (as suggested) and then make liquid doses from it.

For you I would still make a 1M KNO3 solution:

18 tsps of KNO3 (or 101g)
1 liter of H20
mix well

Dose 9.3ml of this to your tank to reach the target 5ppm level.

Sorry for all these crazy numbers Cela! One of the good/bad/ugly things about this hobby is the need to, sometimes, crack open an chemistry book.

>Sarah

[CELACANTHr]

YAY! That makes a LOT more sense! Thank u thank u thank u!