Koi pond

I have never kept koi or even had a pond, so this is all new to me. I have an aquarium so have some experience with fish keeping. I am looking to make a koi pond in the future, the plan is for it to be 13ft x 7ft x 6ft deep with a viewing window. It will be 2 - 3ft below ground and the rest above. I have read conflicting information some say solid concrete blocks on their side are fine, other say you need hollow concrete blocks with re-bar. What kind of filer,pump, and bottom drain is recommend ?