I live in zone 7 (MD) and was toying with the idea of leaving
the waterfall running all winter. My brother-in-law has done
so for the last two years with no apparent ill-effects. Whenenver
the pump shuts off, the water drains out of the lines (all run
down hill) so I'm not sure a power outage would have a major
impact and i think my waterfall edges are high enough to keep
water from changing course as ice forms. Is there anything else
to be concerned with? Would that be good or bad for the fish?

Zone 7a here. I've already removed my WH & WL, it gets mushy after frost
and is harder to remove, imo. YMMV.

Leaving on the waterfall, depends a lot on your waterfall rate. I'd never
leave mine on as the current would be too much for the fish in winter mode.
Whereas I have a friend with a more lax-a-daisile waterfall, that wouldn't
disturb the residents. There is that cooling affect problem as Jim &
Phyllis mentioned. Then there is also the "what-if-something-goes-wrong"
when it is freezing out. Maintenance in winter can be a .... b.... ad word.
~ jan

See my ponds thru the seasons and/or my filter design:
http://users.owt.com/jjspond/

~Keep 'em Defrosted~
Tri-Cities, WA Zone 7a
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