Pond Plan
It seem that my Koi pond is happening in between life.

Thanks Birdman and Dave for your input.

Updated spec.

Loop 1
skimmer/Mid water pick up>Leaf basket (big one)>small pump>(provision for backup BIO)>solar heater (bypass)>split foam fractioner/Algae scrubber (Please read BIO filter)>small pond 3 TPR (circular flow)>Fountain to big pond
Loop 2
2 x 4” BD> 500g SC Vortex>5000 gph big pump>fines filter vortex?>big pond 4 TPR (stream flow)

Loop 3
Small pond BD to big pond. This get flushed say weekly as required.

Questions. Statements.
1) I can see the need to run the pump on the BIO circuit continuas as the critters need to breath and eat so loop 1 24*7 no problem. On the mechanical filter loop can some one please explane why it needs to run 24*7. Why can't I just circulate the pond volume say 2 times a day?

2) I will provide back up space for BIO in a more traditional way. What I do not like about the traditional way is it does not treat Phosphate. That is why every body advocate relative large water changes and a small amount also suggest plantings (This will help but plants chosen grow slow and thus have a small inpact).
For these reasons I chose to go with the Algae Scrubber (treat Ammonia and derivatives and phosphate). There is lots of testimonials although negative ones about string algae blooms if the nutrients are there even in small amounts. The scrubber just grow the algae in a controled way out of sight.

3) Brushes I see them they sound good. But I do not see them on lots of setups. Help here please.!?

4) What is kaldnes?

5) Do I need a air pump can I not return water through the middle of my BD in an upward direction?

Please help me understand the consepts or why my ideas are bad ones.

Thanks.