Ya ha that is true even though some people on here say that certain fish need huge tanks because the record fish of that species got that big. Not often to occur nor will it ever occur in a home aquarium.I'm gonna say a 4' Koi is like a 18'' Oscar. They don't exist. Koi do get large, but they will not get bigger than around 30''.
The pond the OP is building is 3' deep x 3' wide x 8' long.
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