I would also not suggest a 5 gal
bucket unless it's an emergency. Although a decent amount of water for a small fish, the pail is tall rather tha long and surface area is very limited. This can easily lead to low dissolved O2
as well as hard to maintain ph
levels. I would suggest a trip to the hardware store and pick up a cheap rubbermaid bin instead.
The airstone will not really provide much in the way of aerating the water either. You actually need to move the water and break the surface. That is how it will become aerated properly. A heater is a must as well as something to provide for filtration.
<< is a really good article on how to set up a cheap easy to do QT.