Lowering the salinity fast is not a problem(for fish), raising it is. With hypo treatment, you have to be ON THE DOT at all times. It can't waiver, there is minimal room for error.

Those fish in a 20g? hell no

I can't keep exact salinity without a little bit of a swing due to evaporation, so I use Chloroquin Phosphate. It has worked every time, has a wide therapeutic range but is untestable. It's a one and done treatment and takes 2 weeks but I go 3 weeks... just cause.