The house we bought a few yrs ago had a pre-existing pond. It's about 25' wide x 50' long by 12' deep (was 14' deep but it's slowly filling in due to how steep the banks are)
I bought and installed a year-round aerator and I dye the water to keep the algae and weeds out. Then stocked about 40 rainbows (most at about 8" long) in Fall of 2013.
Yesterday I pulled a 6lb trout out of it thru the ice...
A small pond like this is really tricky to maintain and manage mainly because the placement of the aerator, timing of when it runs and doesn't run, summetrtime heat waves and super cooling in the winter are all things I have to worry about constantly. I bigger, deeper pond with properly sloped banks is less finicky.
My next pond, one day, will actually have some thought put into it when I build it.
But in the meantime the fruits of my efforts are trophy sized rainbows. Having a stocked pond is a lot of fun