I'm considering a skimmer and the no niche skimmer looks interesting. I see
that some of you have this gravity fed (Jan), which suits my needs. But I'm
wondering how much suction this will generate and how it is effected by
water depth, etc. (Physics lesson required) I will likely have about 3000
gph split between the bottom drain and skimmer.

Also I imagine the skimmer should be as far away form the waterfall as
possible? How do you deal with the freezing issue since the pipe to the
bottom drain will funnel cold air to the bottom drain pipe? I had planned to
run the pipe from the skimmer outside of the pond to minimize leakage, but I
suppose the inside route might solve the freezing problem.