This is an old thread but thought it might encourage others who are considering a “pond”. I got a small (9 gal) 27” black plastic, fish safe pond from a big box store (currently $17.50) and am going on four years with it now. I hid the top edge with flat stones and added stones in it to provide ledges for the frogs to sun and to aid any small mammals or insects that might fall in to get out. I put it smack dab in the middle of my vegetable garden. Since installing it it has had resident frogs and sometimes toads which not only eat any mosquitoes but also can be found hunting in the raised beds.
I use a small floating solar floating fountain, but the saving grace for me has been water hyacinths. I buy a few in early spring and in a few weeks have some to share with neighbors. They are very prolific and I dispose of what I don’t need the rest of the summer. They are only 3/$8 as opposed to water Lillie’s at $28 each. They have an amazing root system that filters the water and the water is always crystal clear and has never smelled with them in there.
I provide shade for the frogs with water iris, snow in summer and cosmos. I tried water iris in the water, but found they were happier on the outside of the pond. I also use a small floating solar floating fountain that adds a soothing water sound.
Because it is in the center of the garden it is no trouble to “top it off” as needed as I’m watering my plants.