Posted: 27/09/2017 at 22:21
Leaving aside what you put in it, planning a Wildlife Pond is a nice problem to have. I run a large, mature pond (Koi, Rudd, Tench, Goldfish) but if I were setting up a small, quick, WP from scratch I would go for a plumber’s plastic(*) Header Tank, about 3 x 2’, 18” deep, set into the ground, with turf to the edges. Turf helps amphibians come and go. Add bricks and rocks to create a shallow end so you can watch birds having a bath (make sure you can watch from your window). You could even cut an edge in the tank and overlap to another and using a pump, create a flow circuit. I had a friend who did this - the top tank was choked with creepy crawlies and plants - a great natural filtration system, while the lower tank had fishes. You could add a small fountain if you like a bit of bling. Maybe link shallow tank to deeper tank with a ‘stream’ lined with concrete or vinyl. At 18” deep you CAN grow small Lilies (I've done it) and also loads of plants that encourage wildlife. I say just go for it. Experiment, watch what happens, learn, then tweak it to emphasise what you like. It's not a once-only scenario. LIke any garden you can change things. Within a year or two, you'll be an expert, tweaking your pond to suit your preferences.
(*) Before I get flamed on industrial plastics leaching hydrocarbons, volatile compound contaminants, destroying wildlife habitat and environment, I should add I helped a friend with this very project. It has been wildly (wild-lifely) successful for ten years. Not a mutant toad in sight and so many Blackbirds wanting a bath he's thinking of installing a Take-a-Ticket and wait for your number system! So spare me the lectures.