death of fish

Question
Chris,
My fish died last night and I have no idea why. I was worried after I changed
her water. I had her in a 2 1/2 gallon tank (goldfish). I noticed that she would
stick her mouth out of the top of the water as if she was trying to breath
which doesn't make sense. I thought maybe the water was too cold so I
warmed it up and nothing changed. I thought maybe there wasn't enough
dissolved oxygen but I've changed her water many times and there was never
a problem. Do you know what the reason could be?

Answer
Hi Chris;

That's a shame. I'm sorry he didn't make it. Goldfish are just too large and messy a fish to be in a tank under ten gallons. Even a ten gallon will be too small eventually. If your fish has grown at all since you first got it there will be more waste and lower oxygen as waste and carbon dioxide levels increase with his size. Goldfish grow to be over 8 inches long and are very messy even while small so they just need plenty of space and good filtration. If you decide to get another fish get a larger tank and your new fish will do much better. Here is a good web page about goldfish and their needs to help you more;

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

At Your Service;
Chris Robbins