I used the calculator last when making my dosing solutions. I weighed an amount of KNO3, then added water 10ml at a time until it all dissolved. Then I went to the calculator to figure out how much 1ml would change my tank.
This is something I think should be a part of the calculator:
Salt: Maximum solubility at 20C
Potassium sulfate: 1g in 8.3ml water
Potassium nitrate: 1g in 2.8ml water
Potassium monohydrogen phosphate: 1g in 0.67ml water (VERY soluble)
Here are some others that might be useful:
Magnesium sulfate heptahydrate (Epsom salt): 71g in 100ml water
Calcium chloride (anhydrous, dihydrate, or hexahydrate): Extremely water soluble
Note that these are for dissolution in ion-free water. As an example, in the case of the potassium sulfate, its solubility is significantly less as the amount of KCl increases.
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.