fighting fish with white fin

Question
Hi I have had a fighting fish for about 3 months, he seems happy enough, eating well and very active. recently his top fin started to turn white, my local pet shop advised putting some rock salt into his bowl. this i did, but the whiteness seems to be spreading (almost like he is turning grey). he doesn't have any white spots on his body just the whitening of the fins. can you help.

Answer
Hi Tracy,
Your betta seems to have fungus.  Do a 50% water change, and treat him with Maracyn2, or Coppersafe.  Never overdose, always use the right dosage for your betta.  If you must raise the temperature of his water, do this very slowly.  One degree each day, never bring the temperature up fast, as this could kill your betta. To be truthful, I have never heard of rock salt, or maybe I misunderstand.  He should have aquarium salt added to his water. (1 teaspoon to 5 gallons of water.  Maybe the rock salt does the same thing as aquarium salt.....if so don't add any aquarium salt.
Hope this helps, and that he will recover quickly.
Lynda

Hi again Tracy,
I found out what rock salt is, and it is the same as kosher salt, or Nutrafin Aquarium salt.  It is one teaspoon per 5 gallons too.  Sorry about that, but living in a french area, we only have Nutrafin salt here, so I wasn't sure what you meant by rock salt...now I know.
Have a Merry Christmas, and a nice holiday season.
Lynda