question about gravity fed filter

[bphung]

Hi everyone, I am in the planing stage for my pond about 5000 gallon, I want to build a gravity fed filter for it. I really like the design of Skippy 55 gallon barrel from the DIY section. However as I noted all your filters are above ground level and behind the pump, probably a submersible pump. The system I have in mind use bottom drain and skimmer gravity feed water into one or series of Skippy 55 gallon barrels placed underground to filter out all the stuff before they get to a Sequence 5000 GPH pump, here water will be push into water fall. My question are:
1. With just gravity feed, will the water current's velocity fast enough to create the vortex effect to make this filter work?
2. if I have multiple barrels link together like Dr.Case design
https://www.gardenpondforum.com/building-55-gal-biological-filter-t2531.html
I imagine this system will also have a lot of restricted flow, will the water replenish fast enough at the end barrel to supply the 5000 GPH pump?
3. For the above filter, how many barrels link together to make adequate bio-filter for a 5000 gallon pond? The more is better but how much is enough?
4. Where can I place a UV clarifier? Before or after Bio filter?
Thanks everyone and have a wonderful ponding season!

 

[addy1]

Here are some links that might help you

http://www.buildapond.co.uk/pond-filter/bottom-drain.htm

http://www.angelfire.com/home/drttk/information/diagrams.html

http://sacramentokoi.com/Display_Files/PDF/10000.pdf

I tried it with my arizona pond, but did not have it set up right, never did work sigh.

All is starting to grow here, nice and green

 

[bphung]

Thanks Addy!