Indoor Pond Filtration

[Birdman]

Instead of continuing the old thread which has been changed considerably I thought it better to start a new one. The wife reach an agreement on Decor, Furniture and Filtration. I will forget the Advantage system I so dearly wanted and use all the free tanks I just got, and forget a new filter area next to the patio. She gets her new patio furniture and I get to enlarge my existing filter pit from 10 by 20 to 10 by 24. I also get to run water and propane to it, and foundation, walls, roof, and maybe even heat. A pretty good trade off I think.
The pond, patio, and sunroom will stay the same. (1st picture), the filtration is the big change.

Once again the pond will be a oval, about 9 feet by 18 feet, 6 feet deep, 5 to 6,000 Gal.
Proposed filtration, please critique.

Two Bottom Drain circuits, each going through a 4" Bottom Drain, then at the vortexs splitting into two 2" lines, each going to a 24" wide by 54" high Vortex Filter. From there gravity feed through a 3" line to a Mechanical filter, also 24 by 54, filled with brushes, then gravity feed through a 3" line to a moving bed filter, also 24 by 54, filled with 8 cubic feet of Boi Flow 9, spec. gravity .95, air injected by a 40 LPH air pump, then a small pump flowing around 2 to 2,500 GPH will take suction from the moving bed filter and go to the indoor pond water fall. There will be four Votrex Filters total so each vortex will get about 1,000 GPH through it. Once again there will be two of these circuits.

A third circuit coming from a skimmer, to a mechanical filter, 24 by 54, filled with brushes, then to a third pump like above flowing around 2 to 2,500 GPH, then through an 80 watt UV sterilizer, then back to the pond.

The line caring the water from the three pumps will be valved and tee'ed inside the sunroom. There I can divert the flow (around 7 to 7,000 GPH at 5 feet of head) either over the water fall or through the 3 TPS.
Question, if I plumb all three pumps into one common discharge line, how big should I make it? I am thinking 3 inches.

Thank you again all for your help and suggestions. This is a big deal for me and I don't want to mess it up.

[junglegeorge12]

So where are you going to put your bakki?

Just kidding.

The thing I notice was you are splitting a 4" into two 2", that wont work. You will need to use 3".

[Birdman]

Originally Posted by junglegeorge12

So where are you going to put your bakki?

Just kidding.

The thing I notice was you are splitting a 4" into two 2", that wont work. You will need to use 3".

I can do that, just get a bigger uni-seal.
Thanks for the advise.