koi and pond

My koi pond is twenty foot long and twelve foot wide and goes from two foot to a little over four foot deep, and with the small pond and filter contains 6,500 imperial gallons the pond is made of concrete blocks 9"x18"x4" thick, and skimmed with cement and Medusa a waterproofing agent to seal the lime in the cement and also make the walls waterproof. The base is 6" thick concrete, but unfortunately when I built the pond nearly thirty years ago bottom drains where not readily available, so there are no bottom drains. But the water is still circulated from the bottom of the pond to the sump by way of a 5" pipe, which is situated opposite a Ventura so that most of the fish waste is directed to the pipe which comes up the inside of the pond and out near the top, but bellow water level via an elbow the 5" pipe then goes to the sump or settling chamber which is situated about twelve foot from the pond ,the water is circulated to the sump by gravity from where it is pumped by two central heating pumps to the filter which is about four foot above the sump. The reasoning behind sending the water to a sump instead of directly to the filter is the sump acts as a settling chamber, and with a series of filter matting before the pumps stops blanket weed (the scourge of koi keepers) from entering the pumps so that the water flow never slows down and also economics if I had too pump the water to my filter which is about twelve foot from the pond I would certainly have to use larger pumps costing more to buy and certainly more to run.

Japanese Koi are the most beautiful of fish and can live
for many years, the records state that in Japan the oldest koi called Hanako died on the 17th of July 1977 after living to the grand old age of two hundred and twenty six years .
NISHIGOI (their Japanese name) are the national fish of Japan, hundreds of years ago in the Niigata Prefecture the village fish farmers noticed a red carp swimming along with the black carp called Magoi, which they raised to supplement there normal diet of vegetables and rice, and with the passing of time the Japanese breeders have through selective breeding created the many varieties we have today, which are often referred to as Living Jewels.