Newbie New Build

[Golden]

Being new to this Koi pond carry on, I would like to ask for some advice for my filtering system. The pond I am building is around 12,600 litres and 2,772 uk gallons and all dug out by own hands, ok so the questions I have are:-

• I am looking at fitting a 4" bottom drain with a reducer down to 2" which will go in to a 220 litre plastic barrel with the pipework positioned to create a vortex filter, will the reducer give more pressure from the bottom drain to the barrel.
• From the barrel I was going to fit a dry pump (Varipump 30,000 LPH) which will pump in to a compact sieve filter to take out anything that the vortex misses
• After the sieve, the water will be going through a Oase Biosmart 36,000 and from there to either a waterfall or to a bacteria shower filter.

As I say I am very new to this and did ask some questions on another Facebook site, but some of the comments I received were not that helpful and some people forget that you have to start somewhere. Thank you for your patience and look forward to your advice.