I make the pond the settling tank. Crap in the pond has to settle first in the pond in order to get to the settling tank where it has to settle again. Makes little sense to me.

I use a sieve filter instead of the second settling tank. Sieves remove crap from the water column 24/7, are basically self cleaning, take up way less space, cheaper, easier to DIY.

imo the longer the settling chamber the better.i have a 4 ft.x4ft 3 ft. deep on my 1/4 hp performance pro.i would go with at least a 1/2 hp, the performance pro is the top of the line pump.make your sc at least 5 ft. long.run 3 4in. pipes from the pond to the sc so you dont suck the sc dry.