What does aquarium water mean in practice?
The parameters are selected according to the species, the stage of biological maturation and the method of remineralization, not to one universal range.
When does it matter?
A sudden change in temperature, GH, KH or conductivity may be more dangerous to the stock than a moderately different but stable value.
Which solutions are related to it?
Water for water changes is prepared in advance, key parameters are measured and changes are introduced gradually.