vertical swimming and fuzzy

Question
My daughter was given a comet goldfish about 2 weeks ago.  I transfered "Goldy" to a 2.5 gallon tank(water stood for 2 days and was treated prior to transfer) with a bubbler, it is the only fish in the tank.  It has been very happy, surfing the bubbles, etc, until today.  I noticed it has been swiming vertical, up and down over and over and over, and has a gray fuzz all over.  Of course, the pet store is closed and I know next to nothing about fish.  Instead of aquarium salt can I use some Kosher salt just until I can get to the pet store tomorrow afternoon, will she die by tomorrow, HELP!
Thank you

Answer
Hi Priscilla;

The tank is just too small and she may have developed an infection too. Change 50% of the water right away. You can use kosher salt as long as there is nothing else in it. It must be pure salt. Get a medication from the fish store such as Maracyn, Maracyn Two, or Tetracycline to treat the infection. I think it's probably columnaris, so here is a web page about it;

http://www.aquatic-hobbyist.com/profiles/disease/freshwater/columnaris.html

Here is a web page about goldfish care and basic needs so you know what size tank to get;

http://www.firsttankguide.net/goldfish.php

At Your Service;
Chris Robbins