My black moor has a white ring on its back

Question
How long has your tank been set up?4 weeks
How big is your tank?              8 litres...so about 2.1 gal
What type of fish?                 1 black moor
How many fish do you have?         1
Type of filter?                    under-gravel carbon with floss
What are the pH, ammonia, nitrite levels?  1 don't know
How often do you change water?     once a week    
How many gallons of water are replaced every time?  1

My black moor has a white ring on it's back which started a few days ago.  He stays mostly at the top of the tank and has gone off his food.

I've treated the water with White Spot solution (not sure of brand name), at the suggestion of my aquarium supplier, but the spot hasn't gone away.

Should I do a mid-week water change?  Should I put him in a salt solution for 15 minutes (as I read on a different web site)? I'm scared of stressing him.

Please help.

Answer
Hi Rebecca;

I think it's probably a bacterial infection, Columnaris. He needs antibiotics. Columnaris often first appears as a white patch that looks like a saddle. Here is a web page about it;

http://freshaquarium.about.com/cs/disease/p/columnaris.htm

Even after he recovers he will not stay well in such a small tank. It has also gone through the break-in period and that alone is very stressful. Goldfish are very messy fish that get very large. Just for one you need to have at least a 40 liter tank (about 10 gallons). Make a 25% water change at least twice a week until you can get a bigger home for him. He will love you for it! Use the gravel and decorations from the old tank so the new tank doesn't go through a severe break-in. Here is a web page about goldfish and what they need;

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

Here is my page about new tanks;

http://www.xanga.com/Expert_Fish_Help

Good luck and I hope he feels better soon...

At Your Service;
Chris Robbins