You should be careful buying fish like that, try to do all those things you listed before you buy it, it helps in the long run. Best of luck with your new Fish.
if you want this fish to survive ur gonna want to add a bit of marine salt (starting at 1/3 strength salinity is good). what size tank in this fella in? these arnt really ur average aquarium fish
ask puffer punk for all the info i just got a GSP 3 weeks ago they are real picky with nitrates so water changes water water changes water changes.........