pleco are TROPICAL fish, they can "survive" most summers in the USA but wont survive any winters in an unheated pond, the few that do are alive but they dont THRIVE.
please dont do a pleco with cold water fish, its like taking a snowman and putting him in florida in mid summer...just because he doesnt turn into dust like a vampire would, doesnt mean hes going to thrive in that environment.
he needs a min of 74 degrees YEAR ROUND.
also fish of carp type (koi and goldfish) are high output incredibly messy fish, even in a huge thousands of gallon pond, pleco are much too sensitive to those amonia fluctuations to do well...
ill have to try and get some pics of ours, weve got a "mixed" pond, that currenlty has 3 koi, a couple calico shubunkins, some red and whites and some standard comets, hoping to add a trio of butterfly koi and some more spotted shubbies in the spring.