"k conover" wrote in message
...
I know not everyone follows this rule; I've just been told by the owner of
a
major water garden designer store/installer that in order for them to
thrive
(live their full life span, have less disease problems, etc) koi should be
in a larger pond.

snip

Realistically, you could raise Koi in your kitchen sink, if you kept the
water clean and free of toxins. The larger bodies of water that we discuss
for Koi, a la the 1000+100 gallon rule, is to allow for buffering and
chemistry swings. A spawning's worth of Ammonia is much more toxic to a fish
500 gallons then to a fish in 1000 gallons.

The 1000+100 gallon rule provides a rule of thumb that assumes you do not
have perfect conditions, perfect filtration, etc.

BV.