leave empty or with water below skimmer?

[andi_mn]

hi all, i imagine quite a few of us northeners are all going to be doing the same thing on this gorgeous day...finishing fall cleanup of yards, gardens, and, of course, ponds. i am going try something diff with lilies this yr (my overwinter success rate is not very good) i am going to leave them potted, cut back to about 2" and put in water in the basement with water just covering...what do you think?
anyway..my real question is..we have two smallish ponds, one is a little preformed  that sits in a corner of the deck (so sweet) and our bigger pond..liner, skimmer, biofalls. we have pumped the water out to catch the fish, pulled the pump and both are sitting empty. i think they should have some water in, in the bigger pond at least up to the skimmer and the little preformed one maybe 2/3 full to allow for ice expansion. my question? better with water or ok left empty?
just looking for opinions although it's warm enough that i could pump water back into them today. had a great blue heron here for the first time this year, he took my biggest, oldest (16 yr) , prettiest fantail goldfish. and quite a few others. i am already looking forward to next year..waterlilies, couple of new fish, warm days.....it's going to be a long 5 months...sigh, andi

[Mikey]

What hardiness zone are you in Andi?  I don't need to winterize here but knowing your zone will help others with giving you advice.  -Mike

[andi_mn]

hey mike, i forgot, duh. icky, way too long winters, way too cold northern zone 4. many days teens below zero, a few in the 20s below. pond freezes solid to the bottom. i am SO jealous of all you ponders in warmer climates. but we make do and really enjoy our TWO beautiful days a year, .  andi

[Esther]

I would leave water in the pond for the same reason people leave water in a swimming pool. The pressure of the water and ice pushing out will hold against the pressure pushing in, of the freezing soil. Our pond doesn't freeze solid but the water level is up almost to the top of the skimmer which is a household laundry tub, made out of plastic. And in Michigan, the water does freeze but don't know how thick the ice has gotten.

[karen J]

We're in N. Illinois, a solid zone 5a. We're lucky to have run our skimmer pump with a nearby DIY deicer for the past few years, but there is always some issue in Jan or Feb where the temps get so cold that something stops running and we're out for a week or two. I'm afraid to drain the skimmer because of the heaving, so have left that system on. If you are bringing the fish inside, it may be better to have a full pond of water to equalize the pressure. In your small pond, you can float a log to absorb ice pressure. Some people in this forum (years ago) used pieces of foam insulation floated on top of the pond. Could also do the same thing on your larger pond.

I wonder if leaving your skimmer & biofalls empty would be potentially damaging? Keeping it full would be bad, keeping it empty would also be bad. You could cover with a fake rock? Or you could try keeping it running (with a backup pump available, deicer, and really hot water if things get bad.

My ideal situation where I live would be to place a deicer in the skimmer, and a deicer just outside the skimmer, so the system could run all winter. The wildlife loves running water.
Several predictions I've read about say that we'll have a really cold and really snowy winter because of La Nina.
We shall see! 

[Esther]

I again would think you need to equalize the freezing ground pressure and the freezing ice pressure.