Originally Posted by shalu
While estimate is needed when using volume measurements like teaspoons, we should be able to calculate EXACTLY when using weight measurement like grams,
Here is my pure math exercise:
KH 1 degree measures 17.9 CaCO3 equivalent. CaCO3/NaHCO3 = 50/42
therefore 1 deg KH = (17.9/50*42 = 15) ppm NaHCO3.
1 gram NaHCO3 in 10 gallon water = 1/37854 = 26.4 ppm = (26.4/15=1.76) dKH
hmm... quite a bit off from Rex's estimate(1.76 vs 1), but I can't find anything wrong with my math. Comments from experts/chemists?
Shalu: You didn't convert the calcium carbonate to sodium bicarbonate correctly - it takes 2 bicarbs to equal one carbonate. Not sure what happened in the last step either, so I'm going to type it out with all the units:
17.9ppm CaCO3 = 17.9mg CaCO3/Liter * 2 moles NaHCO3/1mole CaCO3 (reactivity equivalent) * 83g NaHCO3/100g CaCO3 (corrected to reflect molecular weights) = 29.7 mg NaHCO3/Liter (double the answer from above)
10 gallons water * 4 quarts/gallon * 1Liter/1.0567 quarts = 37.85 liters
To raise the 10 gallons by 1 dKH:
29.7mg NaHCO3/Liter * 37.85 liters * 1 gram/1000mg = 1.12 grams NaHCO3
It takes 1.12 grams of baking soda to raise 10 gallons by 1dKH (0.112 g/gallon-dKH) NOTE: Maybe this is where the error comes in - someone saw 1/1 and thought it was 1tsp/1dKH - it is really about 1g/1dKH in 10 gallons!
Since Rex did an excellent experiment, we can say 5 grams baking soda = 1 teaspoon, so 1 teaspoon would raise 10 gallons by 4.5 dKH (5 grams/10 gallons * 1 gallon-dKH/0.112 grams).
I use a rough teaspoon of baking soda per 15-gallon water change on my 72-gallon tank to stay about 4dKH.
72g bowfront planted, CO2, 4x - T5HO, Eheim 2213 and 2217, 2 angels, pristella tetras, blue tetras, betta, albino bristlenose pleco, albino cories. Sword, vals, hygros, ludwigias, java moss and fern, anubias
2g Mac-quarium. Clown gravel, fluorescent plastic plants, and 2 guppies.