Oh my gosh!!!!! You have gone all-out! If you are a beginner, holy moly, you are ambitious and impressive! This is so great!
Thanks. I'm not yet a successful ponder though. So keep that it mind. I've only had water since July and fish since September. I had that little "pond" circle thing with the statue in it for about 5 years. No filtration at all. Had some goldies and they lived, but algae got out of control to where it was just an eye-sore mess. Thought I'd make it a bit deeper, add a UV light and skimmer and all would be good. And this is where I ended up. LOL. a far cry from my initial intent.
I know you are excited to get your materials. I'm sure your pond will be very nice and a joy to you for years to come. Be careful handling rocks. They can hurt you!
A word of warning. Folks on these forums will convince you that you need more or different. Some (certainly not all) are down right ruthless when critiquing a design. That is what happened to me to some degree. However, there are plenty of successful ponders that have small, simple pond designs. So, don't let the nay-Sayers discourage you.
Having said that, their experience is invaluable. Just try to read between the lines on what is being suggested and what it offers over your chosen approach. A lot of it has more to do with how much work will be involved in maintaining your pond. I talked to several ponders that don't have bottom drains and they all have to periodically drain and clean their ponds, or use vacuums. And I think that's OK if it's OK with the owner. Same on your filter. You are going to have to take it apart and clean all that media from time to time. A lot of people do this and are good with it. It works for them. A solids prefilter would be helpful to reduce that burden. Many of the "purists", that raise koi for show or sell will advise you to do what is "ideal" for the fish. I had some tell me I should spend $4000 for a rotating drum filter. Is it the "ideal" filter? Probably the best available today, yes. But I wasn't going to drop that kind of cash on one filter. I do love the ultra sieve alternative to the RDF, though. However, these must be set at pond level, which means underground if you don't have a raised pond. That led to my filter pit. And it snow-balled from there. You can see how it gets out of control real quick.
Of all the features I put into my design, the bottom drains were the smartest. My pond bottom stays clean. The bottom debris collects in the sieve and it takes about 30 seconds once a week to hose out the sieve into a bucket. None of that mess makes it to the biofilter. So the biofilter never requires cleaning. And the debris doesn't sit in the bottom for months decaying into toxic chemicals. Gravel filters work great at removing fine solids (sediment) and are an easy DIY project. These are the same as a sand filter, like that used on pools. A pool sand filter, which can be picked up cheap on Craigslist will work as a sediment trap too, and is an easy add-on. Just keep in mind that these require backwashing to remove the sediment.
I did forget to mention that a UV light is an absolute requirement for algae if in even a little sunlight.
Oh me! TMI, I think. I hope I didn't plant a seed of worry into your pond build. It's going to be great! A lot of people will help you out. Just ask questions when not sure.