I use Brita'd water
I do get algae in the tank , as the tank gets afternoon sun.
I clean it w a brush as best I can , then swish in some diluted
warm bleach , let the container sit for a bit
then rinse throughly
Im careful not to get bleach on the screw on regulator
just in case it affects the rubber gasket.
I do not empty the tank.
if I remember to cover the reservoir w a towel
to avoid the sun , I don't get algae.