Sorry I use google and this thread was pushed out of sight pretty fast
by the demented. I have actually built the filter since I posted this
thread.

Jan, the Skippy guy said the 100 gal Skippy could handle 5000gph if
you use a 4in. closet flange. Now that I have built the filter and seen
the flow it seems acceptable. I have been running water through the
tank without filter media and it has settled out the dirt and rock dust
from construction.

SZP, That was the recomended min. size according to Skippy for 3000
gal. my pond is probably slightly less than 3000 gal.. I would have had
trouble using a larger tank in the area behind the waterfall, so I
figured I would see how well it filtered and add a second filter
elsewhere if necessary.