My goldfish died this past summer, but I was thinking about it and I'm not really sure why. When I got her 2 years ago, I knew absolutely nothing about fish. I didn't even know what ammonia was or that fish produced it. I know a lot more now and I do everything I can to make my fish happy so I don't want a lecture on how badly I treated my first fish.
So here's a little backstory. I wanted a goldfish so I went to Petsmart and bought a 1.5 gallon tank with a picture of a goldfish on it. I thought this meant that it was suitable for goldfish. I changed her water only every 5 months or so because it was always crystal clear so I thought it was clean. Despite these terrible conditions, my goldfish was always eager to eat with no visible health problems.
I felt bad for her so I finally decided to upgrade her tank. I got her a 10 gallon which I thought was plenty since I still knew nothing about fish. I also got a pleco and another goldfish. When I moved my first goldfish into the 10 gallon, she and the other fish there died within a few days.
I know now that they died from ammonia, but my question is how did my first goldfish live so long in the 1.5 gallon? I'm sure the ammonia in there at the end of 5 months with no water changes was much higher than it was after 1 week in the 10 gallon. Why she more resistant to the ammonia in the 1.5 gallon than in the 10?