As part of a Landscape redesign, I am installing my first pond and plan to eventually have a hand full of Koi in it. I'm already breaking some of the rules - it'll be located near trees and will get a fair amount of leaf material in the fall.

My biggest question (among appx. 1000), is whether I need a bottom drain - or a skimmer & bio falls will suffice. (Understanding I will need to perform a cleaning every 2-3 years..)

All comments / input welcome.

"True" koi ponds have the bottom drain, skimmer, vortex, filter, UV, venturis, waterfall, etc. I just have a pump, filter, and waterfall but only two koi in my 1800 gallon pond. "Real" koi keepers think it's a horrible crime if you don't have a bottom drain, skimmer, UV, etc.

Since your pond will be under trees, I suggest making an arbor over it. This would consist of a wooden or metal support structure with mesh draped over it. That would keep most of the leaves out and also deter herons. If you don't net the pond or put up an arbor, then the pond will get a lot of leaves. My pond gets a ton of leaves. It's a LOT of work in the fall to keep up with them. A skimmer will jam with leaves so it would need attention multiple times a day in the fall to clean it out. Bottom drains will also clog with leaves but many pond keepers turn off the bottom drain in the fall and winter. You'll need a good pre-filter that has a lot of surface area to prevent it from clogging. You'll need a long handled net to remove leaves off the pond surface and later bottom. They sink after half a day so it's best to get the leaves twice a day which I try to do before they're out of reach.

It's completely up to you if you put in a bottom drain, skimmer, or whatever. You definitely need a good pre-filter (mechanical filter), biological filter, and aeration (waterfall at least).