I've started extending an existing KOI pond. The original is 6' X 3.5'. I want to make it 20' X 10' with a waterfall and a stream. In the pictures I have the original one still in place until I dig to the proper depth for my KOI. The old well on the side will be a small seperate water feature. The external equipment will be in the root cellar on the right of the pond, power is already present. I want to make the natural grade of the land work for the fall and stream? May need help calculating pump capacity for that height and length. Currently I just purchased the house and have my KOI in boarding. They will not fit in this pond as it is. I have 11 KOI ranging from 11" to 2 feet. I built my first KOI pond 5 years ago in my old house (the last picture). I learned what I should have done and hope not to make the same mistakes again? Always looking for suggestions and comments so please fire away. There have been post on a bog filter? This is new to me, is it worth it? I haven't decided on a filtration system yet, the last pond was a BOISTEP filter, a 40 watt UV, top and bottom skimmer with submersible pump driving it all. I need to step it up with this one because I worked to keep that one clean and would like to enjoy this one.