dosing in a 4.8 gallon is counterintuitive, not my opinion, but its a consensus in the hobby.
if youre unhappy with low alk levels the salt youre using is most likely designed to be at a low alk. changing that is how you can raise alk levels, rather than artificially buffing it up which will disrupt so many other natural processes, amplified in a 4.8 gallon pico.
remember this “nothing in this hobby ever happens by not doing something, - but by doing something” , (unnecessary dosing being a prime example)
acans and duncans are two of the easiest corals and if they are dying then that should be a loud indication that something you are adding to the tank is messing it up,
