Making a small pond out of a flower pot?

There's TONS of people doing this on Youtube with goldfish and such. I want to try my hand at it. And don't worry not with gold fish. With mountain minnows or roseys. Yes it will have a filter cleverly hidden in a water feature that will be attached to the pond as soon as I find out how to do it. I want to use a large-ish 20'' ceramic flower pot and put lots of plants in it so that it fits in in the garden. What's the best way to do this.