Planted Tank Enthusiast
Join Date: Feb 2017
Location: Lindenhurst, IL
Also, reaction kinetics are proportional to the concentrations of the reactants. Because of that, the increased volume of the whole aquarium would make the same amount of acid and bicarb react slower.
Other acids could certainly be used, but citric acid is a triacid that is fairly efficient with respect to acid equivalents to weight, and because it is available as a crystalline solid, it is easier to handle and less likely to burn you with contact or fumes.