Sheltered pond clearing

Hello all,

My pond is entering it's first winter and I have covered the pond with a
a shelter made of irrigation pipe and plastic with a ridge beam to carry
the snow load. Inside I mounted a light fixture aimed at the waterfalls
about a foot above the water with a 250 watt spot light in it on 24/7
The temperature at night here in BC has been -10 celcius or about 14
degrees farenhight but the shelter has yet to go below freezing inside.
The water was at 42 degrees farenhight when I put the shelter up about
3 weeks ago. It has risen to 48 degrees farenhight in the three weeks,
even with cold weather (uncovered ponds already have a 1/4 inch skin of
ice). As an added bonus the pond over the period of the last week has
begun to go crystal clear, up till now it has been hard to see a fish 6
inches below the surface. Now you can see the roots of the lilly in the
4' area (as well as all the fish).
I do not have any pictures showing the shelter but the pond can be seen
at http://www.boundary-ca.net/pond/index.html

Don - Southern BC