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
