Time you enjoy wasting is not wasted time. ---- Marthe Troly-Curtin
KoiRun on YouTube, latest video:
https://www.youtube.com/watch?v=PmiHmpbWEOY&t=170s
I've got a theory, not really original, that every two years, a koi approximately cuts in half the amount that its length will increase in the rest of its life. Of course, not all koi follow this growth pattern. But a two year old would be about half its ultimate length, and a four year old would be about 75% of its ultimate length. 22.5"/.75 = 30". So it might get pretty big in several more years.
Too bad he's unsociable. Makes sense to re-home him. The soragoi / chagoi / ochiba types that I've had have been some of my most tame fish.