Welcome to TFK and the wonderful world of
Goldfish. I noticed that your avatar is a betta.
Goldfish are very different from betta. Trust me. I have both. My first question is do you have a fancy
Goldfish (double-tail) or a common
Goldfish (single-tail)? There are some differences in care depending on which one you have.
If you want a larger tank right now, you can buy those large plastic containers that places like WalMart and Target sell. They are great temp
Goldfish homes.
Goldfish do best in groups, so once you have a larger tank (probably 40 gal or 55 gal tank), you should get your
Goldfish some
Goldfish friends.
As the others have said, understanding the nitrogen cycle in a
Goldfish aquarium is vital as
Goldfish produce a lot of ammonia. (The test kit is also vital.) The links that Max gave you are a good start. Feel free to ask about anything you don't understand.
In that size tank with just one
Goldfish, you are looking at every other day 50% partial water changes. Turn off the filter and siphon out the debris in the bottom using an aquarium gravel vac (you can find them in pet stores). Make sure the water you are using to refill the aquarium is close to the water temp of the aquarium. Add water conditioner (Prime is great to use with
Goldfish because you need soo little), and then add the new water to your tank.