Hi MFKers, i have spent quite a while reading on this forum and ppl here are very helpful and informative, therefore i have finally joined up....I am from Hong Kong, and have always dreamed of keeping big fish. right now, my uncle, who lives next door is building a pond outside his house and this is the first time we are doing this, so this isnt exactly a DIY but i figured i might post here for some help anyways. So here are some pics of the progress and a lot of questions to follow 
so i was wondering....if we build a filteration/sump thing next to it, how big does it have to be? and does it have to be as deep as the pond? if so, dont i needa cram alot of sponge/ ceramic rings down them?