Hello, my wife and I are new to the garden pond scene and are looking forward to learning a lot from here. This spring we built up a two tier, pre-formed pond alongside our back deck. We use a Laguna maxflo 600 waterfall pump in the bottom pond which pumps up to a Laguna UV sterilizer, and then into a homemade bio filter that I learned how to make on Youtube. The top pond just overflows into the bottom. We currently have 2 Comet goldfish and 4 Koi which I can't remember offhand which type they are. I'll post a couple pics to get us started.