Take a look at this beautiful koi weighing in at 91 lbs (6 1/2 stone).   A fun, short article on largest koi in UK. 
 
A British fish fan has taken delivery of the world's biggest koi carp - a 4ft monster that tips the scales at a staggering six-and-a-half-stone. The mammoth fish - nicknamed the Big Girl - is the size of a 12-year-old child and three times larger than any other carp in the UK.
 
British fish fan splashes out on the world's largest koi carp | Daily Mail Online