It has everything to do with your tank goldfish have a huge bioload.
If you just want to keep a fish in a bowl I would suggest a Betta they are a
Labyrinth fish and they breath at the surface so they can do quite well in a small
Tank with frequent water changes to remove the waste. Gold fish are a hearty and
forgiving fish that can adapt to a lot of circumstances but ideally they need
At least a 30 gallon tank with a good filtering system. You can probally have some success
with one in a bowl for a short time but I honestly think your setting your self up for disappointment.

Update:

The goldfish is still alive. It's soo weird. I think it's a shy swimmer because when i walked back into my room it was swimming but when he noticed i was there, he was back at the bottom. lol .
we'll see. I was also perhaps thinking the white one is a male and the gold one is female? but i don't know...

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