Generally speaking when trying to help someone with a sick fish, it is best to get as much information as possible before diagnosing the problem.
Water parameters, water change schedule and volume, additives, etc.
Please read the pinned topic at the top of this forum:
http://www.fishforums.net/threads/start-here-with-your-emergency.422952/
Helpful information to include:
You may cut and paste the template below and submit in your post:
Request Help
Tank size:
pH:
ammonia:
nitrite:
nitrate:
kH:
gH:
tank temp:
Fish Symptoms (include full description including lesion, color, location, fish behavior):
Volume and Frequency of water changes:
Chemical Additives or Media in your tank:
Tank inhabitants:
Recent additions to your tank (living or decoration):
Exposure to chemicals:
Digital photo (include if possible):
And for members offering help...
A Word on Advice
A word to all of the helpful members who assist others when they are having trouble : Please don't advise someone to treat or medicate a fish unless you are certain of what they are dealing with. I'd like to point out how important it is not to steer someone in the wrong direction, especially at a moment when they're desperate.