So I purchased my home 3 years ago and it came with a koi pond. Sounds awesome. Unfortunately the more time I spend here the more I realize I have a frankenpond. The former owner was a handyman and he built the pond himself. The pond works fine but is nothing like your ponds. It has tons, literally, of rocks and boulders in the pond.
I looked at the pump today and saw its a Monarch BSE 100lp pump. I have no idea what that would have been used for. One day i will be asking for help to construct a proper pond.