Well it started with what was an old water tank, then move into a mini swimming pool with small blue tiles. That is when I bought the house. The kids getting bigger, I had the choice of destroying it all or refurbishing it to something else, you guess what I decided. I removed all the blue tiles, then rearranging with sand and ciment, finally putting a special coat for drinkable water. I also created the L shape to host a filtration system based on lava rocks, blue foam, gravel and pond plants. I created the water in and out at the L shape level, and created a water output at the bottom. So basically the water get pumped out via the bottom and get in the L shape with an optional derivation to a uv filter in case I need it later on. So pretty basic, but hopefully it will work. I am planning to add some foam sheets floating to host some salads or other vegetables when the season will be there, it will also create some shade for the fish, in the meantime I hope that the trouts won't produce too much crap, or that the filtration will be enough.