The reason I bring this up is that these bead filter companies like to make you believe that a bead filter is an all-in-one product that can be used as a solo form of filtration, and this is usually far from the case. Now, I know that the Ultima II isn't really a "bead" filter technically, it's more of a pressurized media filter, but it functions on the very same principles. These types of filters are great to have and can be placed anywhere, which is a great feature--and the cleanout method on them is fantastic. BUT, they act more like a fines type filtration and you should still have some kind of settlement chamber in before them. A sieve or barrel would totally work to serve this purpose, and would add an extra dose of a place for bacteria to grow.
I use my barrel technically as a settlement chamber or pre-filter for my pressure filter to pick up the thicker detrius before it hits the pressure filter. I suggest, D&RW, that you do the same. Don't fall for the manufacturer's gab about this being the perfect solution for complete filtration for your pond. You can definitely check other koi forums that discuss these bead-type or open media filters heavily to verify what I'm saying. Also, you will find that many serious ponders are not fans of the open media that is inside an Ultima II because it is prone to clogging and getting trapped in the open chamber of the media. So, it would be super important for you to include a settlement chamber/barrel before this filter to prevent that from happening. You don't want to have to end up opening this thing a few times a year to clean out the media. It would be a total PITA. Or, you could opt for buying closed beads and replace the open media the Ultima II comes with...pricey to do, of course.
When I build my new pond, I plan on using one of these pressurized filters as well, but I certainly will not be getting rid of my barrel and using one as a pre-filter before it at well.