When I moved house in October 1994 it was thought by some of the family that the choice of house was influenced by the 30ft x 20ft swimming pool in the rear garden. However, from a koi-keeping standpoint the swimming pool did not influence my decision to buy the house.
Having moved in I started thinking about building a pond and considered wether it was practical to utilise the swimming pool in some way by building a koi pond within the swimming pool. The pros and cons were these :-

FOR - no digging out, no moving tons of soil and so saving in time, cost and labour.

AGAINST - I would have to work with the rectangular contours of the swimming pool and build a formal pond rather than the preferred informal one I wanted.

Also the swimming pool bottom was a constant slope from the 4' deep shallow end to 6' at the deep end presented a less than ideal situation built of reinforced concrete which would need to be taken up in part to accomodate pipe runs from bottom drains to filter.

Two pumps return water to the pond via venturis on opposite sides of the pond providing a good circular flow around the pond. The larger pump a ½" HP ITT Marlow is situated in a shed adjacent to the pond and pushes water through a 24" sand filter, then a magnet and finally two 30 watt UV's before returning to the pond.

A quarantine pond 5'6" x 12' x 4' deep with two filter bays was also incorporated into the design. The whole layout (except for the vortex chamber) was rendered blockwork and then fibreglassed. The pond build started over the Christmas holidays , and was completed by early May, although the quarantine system will not be finished until next year.

A major koi dealer, perhaps seeking a big sale, recommended that each of the three bottom drains should feed into separate vortex chambers as my proposal to have only one would result in unequal water flows through the bottom drains with consequent reduction in efficiency and build up of waste in the pipe runs with the slower flow rates.

However by incorporating 4" gate valves in each pipe run just prior to the pipes merging and entering the vortex I can purge each bottom drain periodically and pull out any waste or grit that has settled in the pipe runs. This feature seems to run very effectively and highlights just how much grit and dust blows into the pond.

The filters were seeded using Flocor and filter matting from my last pond in Gros Faen. I also syphoned out of the Gros Faen filters a large quantity of underwater animal life which had always inhabited the settlement bay in particular and do, I am convinced, play a valuable role in the overall eco system that is the biological filter. My koi were introduced to the new pond in stages over two weeks in early May and settled in very well.

So far I appear to have avoided the water quality problems sometimes associated with new ponds while filters take time to mature. Long may it continue - or have I just tempted fate.
Happy koi-keeping. Rob.