Asking for the "Why" we can see that there is different intentions behind the different recipees.
The limitation of "how potent" they are, normally are defined by the Alk liquid solution as this salts have the strongest limitation in solubility.
Using NaHCO3 solubility is only 95 grams/Liter. Using Na2Co3 this is 216 grams/Liter. Efficiency of the two salts is different. Also a mix is possible and used in several of the newer recipees (often called KH Buffer)
AF's recipe (the one with 50 grams Ca salt, 80 Alk salt 10 Mg salt per Liter)
- Only NaHCo3 used, 84% (80/95) of the max solubility used in order that customers don't get a solubility problem if eg not weighing accurate
- Ca, Alk and Mg liquid solutions "defined in a way that the user has same amounts of all 3 liquid solutions.
As Mg is consumed only very little, this leads to an etremly low concentrated Mg liquid solution (only 10grams/liter)
- Dosing equal amounts of the solutions is reached if your consumption is eg Ca 10 mg/l per day, Alk 1,32 °dKH per day. Or a multiple for it
ESV recipee
- Pure Na2CO3 (SodaAsh) used with around 68% of max solubility. So, also here customers shuldn't get a solubility problem if self-mixing and not weighing accurate
- Ca and Alk liquid solutions "defined in a way that the user has same amounts of this 2 liquid solutions only". Mg is kept separated
- Dosing equal amounts of the Ca /Alk solutions is reached if your consumption is eg Ca 10 mg/l per day, Alk 1,5 °dKH per day , Mg 0,7 mg/l per day. Or a multiple for it
- Mg a bit more than 315 ! g/Liter of Mg Salt used (ca 20% of max solubility).... much more concentrated than AFs recipee.
