I am building a small pond (about 1000 eff gals) with a waterfall, and
don't have much room to work with. I was orinally going to use an
'upstream' filter with a waterfall weir (Atlantic Gardens BF1500)- but
the size constraints make this difficult to accomodate. Instead I am
thinking of using a pressurized filter. I'm planning on running the
outlet of the filter to the top of the waterfall. The waterfall will
be about 3'-4' above the water level.

I don't want to lay out the $$$ for a bead filter, so I'm looking at
the various pressurized bio/mechanical filters such as Oase, Cyprio &
others.

Any recommendations on the best filter to use in this scenario, and
any experiences using the outputs for a waterfall this size?

I'll be pumping about 1000gph through 1.25" tubing, with a pond
skimmer on the opposite end of the waterfall.

Thanks for your help!