It is difficult to tell the sex on younger Koi, it gets easier as they get
older.
Females tend to have rounder bodies and rounder pectoral fins and their
fins tend to be somewhat smaller.
Males are sleeker, with more pointed pectoral fins, and their fins tend to
be larger.
Others claim the colors of males are more brilliant.
Older males have a sand paper like raspiness on the gill plates, and some
claim you can also feel a roughness if you lick your tongue across the front
of the pectoral fin. If you try this let us know!
The easiest way is when there is a particularly aggressive male chasing
the females, with the proverbial nose up the butt, you look for other males
chasing the same now identified females.
Phone: 303-883-8000