Am I missing anything else here? I doubt it but am open to ideas.
The most and best aquariums are for example in Japan, Hong Kong and Singapore. They use mostly ADA substrates and have very soft tap water. Below are their tap water parameters:
Alkalinity 13 – 61 mg / L, 0.7 – 3.4 dKH
Total hardness 47 – 83 mg / L
Ca hardness 41 – 60 mg / L, 16 – 24 ppm Ca, 2.2 – 3.4 dGH
Mg hardness 6 – 23 mg / L, 1 – 5 ppm Mg, 0.2 – 1.1 dGH
Alkalinity 7 - 78 mg / L, 0.4 – 4.4 dKH
Total hardness 4 – 64 mg / L
Ca hardness 2 – 53 mg / L, 0.9 – 21 ppm Ca, 0.1 – 2.9 dGH
Mg hardness 2 – 11 mg / L , 0.4 – 2.8 ppm Mg, 0.1 – 0.6 dGH
Alkalinity 6 – 40 mg / L, 0.3 – 2.2 dKH
Total hardness 27 – 221 mg / L
Also, they most likely follow the ADA water change instructions which I think is 30% weekly after initial break-in period due to leaching NH4. And I don’t believe they do much testing of GH, KH, Ca or Mg. They only watch for NH4, NO3 and PO4 to see if there is needed an extra water change.
Below is data I have collected from few ADA magazines where we can see actual aquarium water parameters. The data is from 31 Takashi Amano’s aquariums:
TH Total hardness:
8 with 50 ppm, 2.8 dGH
1 with 30 ppm, 1.7 dGH
18 with 20 ppm, 1.1 dGH
4 with 10 ppm, 0.56 dGH
7 with 6.6
1 with 6.4
3 with 6.0
“What constantly fascinates us is the water quality of natural springs. When our field research unit conducted a comparative water quality testing three of the world’s largest rainforest, where majority of the aquatic plants and tropical fishes originated, we discover the water to be rather acidic and extremely poor in dissolved salts. The pH values for the constant varies between pH 5 to 6, with TH averaged below 20mg/litre.”
(ADA Aqua Journal, Vol.36, pg.28), 20 mg / litre = 1.1 dGH
“When CO2 is injected into the water, its pH will be lowered approximately to the range of 6.6 – 6.8. If your aquarium is a newly setup tank using Aqua Soil as the base substrate, the pH will decline further to 5.0 – 5.5 or even lower. There is no cause for alarm as this is only temporary.
After a period of time (about a month’s time), when the substrate is leached by regular water change, the pH will gradually rise back up 6.6 and remains constant thereafter. “
(ADA Aqua Journal, Vol. 38, pg.29)
Notice that there is no mentioning of any KH values. ADA doesn’t even have a KH test kit. The KH and pH buffering is controlled by the substrate. When minerals are adsorbed by the substrate they are not locked up, they are going to be released when needed.