Does a pond need to be at least 36” deep to keep koi?

Millions of healthy and happy koi currently living in thousands of 24” deep ponds serve as physical proof that 36” is unnecessary when it comes to koi keeping.

The Earth’s insulation allows ice to only freeze up to 8 inches thick
This leaves 16” in which fish can safely hibernate over the winter

Building codes traditionally consider 24” to be a landscaping feature
A 24” deep pond also requires less work and costs less in the first place.