Pond fish owners generally fall into one of two camps: people who just want to kick back and watch the pretty fish at the end of a long day, and people who make their fish their lives.
That second type is the one most likely to own a koi museum.
Koi museums are colloquial term for water features designed with the sole purpose of housing fish - usually very expensive ones displayed at very fancy shows. Much like the owner of an expensive show Sheltie, the owner of a koi museum will often invest significant time, energy and money into caring for their koi. They might spend a couple thousand dollars or more on a single prized fish, or create high-tech environments that let them monitor water quality and fish health.
Everything about a koi museum centers around showcasing the fish and keeping them at optimal health. An ecosystem pond, on the other hand, is designed to be low-maintenance, look natural and provide a place for you to enjoy the sounds of water in your backyard (and still give your fish a place to thrive).
Which one you want to build depends entirely on your preference. Splash Supply Company can do both.