new goldfish sick

Question
I bought a new goldfish 3 days ago.  He is a very small shubunkin.  He seemed OK until this morning when I noticed him lolling around near the bottom.  His backbone area between the fin and head is sunken in.  I've changed the water, with proper water chemicals, so I think the water quality is OK.  My other 4 fish, also shubunkins, are darting around and doing fine.  I feed them a small portion of floating pellets twice a day.  I have a 25 gal. tank.  Thanks for your help.

Answer
Hi Kathy;

I'm not sure what could be the problem except maybe he's just trying to get used to his new home. Make sure he isn't being intimidated or bullied by the other fish. Maybe provide extra hiding places for him. If you could upload a picture of him to a free image hosting site such as photobucket.com and send me the link I could take a look at it.

You might want to know that your tank will be overstocked as your fish grow. Shibunkins are Goldfish so they grow to be very large and are just naturally messy guys. Just one needs at least ten gallons of water.  Here is a good web page about goldfish and how to provide what they need;

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

At Your Service;
Chris Robbins