Formal pond construction from a newbie

I'd like to build a 12' x 8' formal rectangular pond on my patio that
would contain a few goldfish and some water plants and I'd like to do
it out of concrete. Our local codes clasify ponds as swimming pools and
as such any pond or pool deeper than 24" is subject to having a fence
put around it. This means my pond will be no deeper than 22" because a
fence would ruin the look. The pond will prodrude 12" above ground with
the remainder under ground and I live in Michigan so this means it will
probably freeze solid in the winter. I would like to use concrete to
construct the form and tile over it with black slate so it matches my
patio and I'm wondering if I can drain the pond in the winter in order
to minimize the chance of the pond cracking? There seems to be a lot of
discussion about leaving the water in the pond and either using a
bubbler or heater to keep the water a liquid but the driving factor in
most of these talks is the need to keep fish alive. I would rather keep
the fish inside where I can still enjoy them especially if it means I
can drain the pond and not worry about it cracking in half over the
winter. My plan is to build the pond with a layer of insulating
foundation foam around the perimeter where it's under ground and pour
the base on top of a 6" bed of crushed stone. The idea being that any
side shifting will be taken up by the foam and any upheaval will be
distributed by the rock bed. Has anyone tried this? Do any of you drain
your concrete ponds in winter?

Please help
Thanks
Todd