I've recently put together the following new system, a real RoG beast:

ASUS ROG Strix Helios
ASUS ROG Thor 850w
ASUS ROG Crosshair VIII Hero WiFi X570 AM4 ATX
ASUS ROG Ryujin 240mm RGB Liquid CPU Cooler
ASUS ROG-STRIX-RTX2080S-A8G-GAMING
AMD Ryzen™ 9 3900X
G.Skill Trident Z Neo RGB 32GB (2x 16GB) CL16 DDR4 3600MHz Memory F4-3600C16D-32GTZNC
Corsair Force MP600 1TB NVMe Gen4 PCIe x4 SSD M.2(2280)
and a ASUS ROG Swift PG349Q Monitor to top it all off.

Throughout the build, I've had some real trial and error issues, in particular, coming up with the best way to install and configure the Ryujin 240.

So I have to ask, what is the best way to set install and configure the Ryujin with the Crosshair VIII Hero?

After quite a lot of experimentation, currently I have the radiator fans plugged into the AIO Pump fan connector which is then plugged into the MB AIO_Pump connector on the MB as per the Ryujin instructions. However, I should note here, the actual instructions included give unclear directions as they give two options, to plug into either AIO_PUMP or CPU_FAN.

However, when checking the instructions for the Crosshair VII Hero MB, the section that covers "To install an AIO cooler" actually recommends plugging the two radiator fans directly into CPU_FAN and CPU_OPT connectors directly and the Pump into the AIO_Pump which is in contradiction to the Ryujin instructions.

I tried this and it worked initially but after a couple of days and a number of reboots, it then stopped working, both radiator fans just stopped turning when plugged in like this and the CPU temps went sky high. Fortunately I noticed this quickly and shutdown the PC and changed things up to how they are currently configured.

Also, to get it to work using the AIO_PUMP MB and not the CPU_FAN connector, it took some tweaking of the bios to actually get it to work with the AIO Pump fan connector plugged into the MB AIO_PUMP connector as I would get that F1 error on boot up saying "CPU Fan Error". I tried disabling the CPU fan in Bios but this didn't work. I did see advice in this forum to;
"In BIOS, go to the Fan control section not the monitoring section. The CPU fan headers should be listed - should show "CPU Q-FAN Control - Enabled or Disabled", Enable that setting. Then you will see the setting below that is "CPU Fan Speed Low Limit", set that to Ignore."

This worked but is less than ideal I think.

So to repeat myself from the start of this rather lengthy post, my ultimate question is; which way is best to setup and configure the Ryujin with the Crosshair VIII Hero?

My second issue with the Ryujin, like a recent post to this forum, is that I am experiencing similar issues with my Ryujin 240 fan control, by default, everything on boot up runs at 100% and the noise is literally deafening.

I've set up profiles in AI Suite / Fan Xpert 4 for all 3 of the the Ryujin related settings: AIO Pump, Ryujin Fan and Ryujin Fan 1. This fixes things and I'm happy with the quiet and still excellent performance.
But... after a reboot, everything defaults back to 100% and the noise is alarming. When I open AI Suite and Fan Xpert I see that all three Ryujin settings return to 100 % flat-line and I have to manually reset and save the settings again. Very frustrating!

One thing I would like to have confirmed if anyone can, in Fan Xpert do the following labels correlate to the specific part as I'm guessing in the following:

AIO Pump is the Ryujin water pump?
ROG Ryujin Fan is the CPU fan that sits on the AIO Pump?
ROG Ryujin Fan 1 is the Radiator Fans?

Another question, is it best to leave the AIO Pump at 100% as I've read differing views on this but the most prevalent view seems to be that the pump is best kept at 100% to get the best lifespan?

Also to throw in my $0,02 worth, Armoury Crate has to be the most frustrating piece of software I've ever encountered. For the Ryujin especially, it continually errors, 2 out of 3 times on boot up, where it says "XML format error. Please restart your system (Status:0 GetCapability)"

And this is after the PC has been booted up fresh which is again, very disappointing!

Honestly, all in all, I love this new PC and all the awesome RoG components. The frustrations of the above don't really take away my overall happiness, but I have to say, the accompanying software leaves quite a lot to be desired. And as someone who runs software development and support teams, I can't understand how this software is so buggy from a company as good as ASUS, especially for their flagship RoG range of products!