Hi Murray, yes nice pond and glad to hear you are bonding with your fishies! I myself was surprised to learn how aware and interactive they are - they will recognize who feeds them and Ive heard of people who actually can reach in and pet their fish!
Koi are large and rambunctious fish, that can grow almost a meter long.... so right there you can see they wont work for a 2 meter wide pond. Its a myth that fish grow only as large to fit the container. The recommendation for koi is minimum 500-1000 gal per fish and a minimum of 4 feet - they need to be able to dive and move freely for good exercise and health. Plus, its just simply more pleasant to watch fish if they can move around in a school. For goldfish its 50-100 gals per fish. A lot depends on your set up and filtration capacity though ( you don't have mechanical filtration but your plants are essentially serving the same function as a filter would. )
Comets and shubunkins are good hardy fish that are good for ponds - looks like that's what you have. They can have different unusual colors and long fins, and closely resemble a koi - except theyll only get 10-12 inches, not 36!