1 Goldfish in a 15 Gallon Tank

[SubRosa]

You can get a 30 gal that will fit on the same stand as the 15. Aqueon 30XH.

 

[ianab]

If you don't have a heater then White Cloud Minnows work great for that size tank, get a whole school of them in there, or even Rosy Red minnows.

Ian