I have a 160 gal pond so I have no advice for you, but I did get a notice from our local pond store that PondMaster is having a mail-in rebate offer from now to June 30, so be sure to check that out if you do get a PondMaster pump (or pumps).

I threw in the word pumps because I know some people have multiple pumps rather than just one humungous one.

I've got a large concrete pond I built about 20 years ago, way before I ever read about what I should have for water circulation I have never filled it through a meter and it has different slopes and terraces in it so it's hard to calculate volume. It is a dogleg about 90 x 35 x 6' max depth. I'm guessing somewhere between 80 and 100 thousand.

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Pond continues to right where I have 3 large bio filters that waterfall back into pond.

I've got 1-2hp and 2-3hp Max-E-Glas II pool pumps. Those were about 150-180 gpm each pumps when they were brand new giving me a 100% turn over every 3-4 hours. Over the years I have put in a manifold that lets me run all of the drains though any single pump or combination of pumps I chose. I've been running just one pump 24/7 for years and I really haven't noticed a difference in water quality versus running all three.
I swim in my pond and I'm able to sweep and vacuum it when I desire. I have 3 large combination sand/gravel basins heavily planted I use for bio filters and a large pool cartridge filter. The bio filters are small ponds themselves and pretty to look at. The mechanical filter is only used a day or two to polish water if I'm having a party.
Pond is in full AZ sun all day. I have fish, frogs, toads and various bugs in pond and bio filters. Sometimes even ducks. I use to curse and jump up and down when herons, hawks, owls and assorted 4-legged critters ate my fish (still do when they get a big one) but I've come to see that mother nature is just helping me keep things balanced.
There are a lot of variables to ponds when it comes to keeping them clean, I'm just pointing out what has worked for me. I think a large bio filtration basin built into your pond would allow you to get away with a longer recycle time. My suggestion is put a lot of thought in piping, bottom drains, skimmers, and a LARGE built in/on planted bio filter. With a little extra piping you could put in a manifold and add a 2nd pump in the future if you needed help with a seasonal/temporary algae or fish population problems.
All that said, I built this back in my "If some's good, more's better" days. Concrete was $50/yd. I got all 3 pumps for $500, the price of just one today and I could run all 3 pumps for what it cost me to run one today.
I'm 20 years older now and wish this was a whole lot smaller.

Holy Cow Tinfoilhat!!! That is one beautiful pond!