Backyard Pond

I thought it would be a cool idea to make a pond in my backyard. Next summer i could plant the lotuses and lily-pads, maybe add some goldfish too.

Here's the area i planned on putting the pond. It would be 'L' shaped and fit in between the wood fence and the concrete slab.
I dug down about 4" the approximate area of the pond. I removed the topsoil, leaving the clay.
Then in Photoshop I drew in what i thought the pond might look like. I added water, rocks, lotuses and a tiny waterfall in the corner. The waterfall would help aerate the pond and i would also filter the water using a homemade first flush filter.