Goldfish fins changing colors?

Question
Thanks for reading my question. I bought a 3 gallon goldfish tank while I was in college and have had one goldfish. I don't know the gold fish breeds but he is definitely not one of the feeder fish that you get in petco. He has a short fat body and long fins. He has been in the tank for almost 4 years now and has been very healthy and active. I change the water once a month and he has a very small filter that came with the tank set up. Bucca(as my niece has named him) has always had white fins but just in the past couple days the end of his tail fins have started to turn a dark red color like blood. He is still very active and begs for food every morning. Is the red color just because he is getting older or is there something wrong with him. My niece has grown very attached and while it may be silly, because he only cost me a couple dollars, I would hate to have to explain to a 3 year old why her fish isn't in the tank anymore.
Thanks for your time!

Answer
Hi Katie;

It isn't his age. Goldfish actually live to be more than ten years old and grow to be over 6 inches long. When you buy them in the store they are under a year old. He just needs a bigger tank right away. I'm so sorry you were misinformed somewhere along the way about what goldfish need. Being in such a small environment for so long has finally taken it's toll. He's certainly a strong fish to have lived so long in there though. Goldfish actually require at least a 10 gallon tank with good filtration just for one. They make so much waste, even while small, that they just need lots of space. All fish need a weekly 25% water change too. A month is a very long time, especially for a goldfish in a small tank.

For now, change 25% of his water every day, using a water conditioner. It will boost his immune system and help him recover on his own, if he still can. He may need medication for bacterial fin rot but the cleaner water more regularly should help him out. Once you get a larger tank for him just see how it goes. If the redness doesn't go away or get better in a couple of days, medicate.  

Here is a good web page about goldfish so you know what size tank, maintenance, and filtration system he needs;

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

I hope he does okay...

At Your Service;
Chris Robbins