Why 4dKh for drop checker?
It seems pretty standard now that you use a 4 dKH solution in a drop checker. But why is 4 the magic number? Is it simply because 30 ppm is what is considered optimal now and that is where the green on the old pH chart falls for 4 dKH?
I don't have a drop checker yet (on order), but it seems that people have issues discerning green from blue in the aquarium. Since 4 dKH could give you anywhere from 19 to 75 ppm and still be greenish, that seems a little dangerous (assuming >40 ppm CO2 is dangerous).
I also read of people looking to use 5 or 6 dKH, but that would mean an even bigger range in the greenish zone.
It would seem to this complete noobie, that a solution of 2 or 3 dKH would be safer. At 3 dKH, anything green is 56-14, with the middle being 30. At 2 dKH, the green range is 10-37, with the middle being 20. Certainly, if you are doing PPS-Pro, it would make more sense to use a 2 dKH solution since you are targeting 15-20 ppm.
Making a 2 or 3 dKH solution would be as easy as diluting a 4 dKH solution with DI water correct? 1:1 DI and 4 dKH would be 2, and 1:3 would be 3 (it is late here so my math here is probably wrong lol).