Yellow Tang is showing redish markings

running a lower salinity, 1.019-1.020 will slow down the spread of parasites in large system and quarantine tanks. Lower salinity; 1.013-1.015 can be used in hospital tanks to fight a number of parasites as well.

 

Possibly, but I'm not sure this is true though at this level. Certainly many parasites wouldn't care less. Also, long term I tend to think it's stressful, I know this is debatable though. I do know of a number of LFSs that do this to save money on salt though. Usually their fish look pretty dull after being in their systems for a while though, although if salinity is part of the reason, I'm sure it isn't the only reason

Sure, hyposalinity can be used in hospital tanks (although usually I go a bit lower 1.010-1.012ish). Again though, personally, I wouldn't do this long term, but that's just my .02.