Overwintering a small outdoor frog pond

[Green Frog Lady]

Hi - I'm a new member of FrogForum and in my first year of frog obsession.

This spring I installed a 5'x7'x18" preformed pond liner in my Maryland yard, put some dirt in the bottom and added some water and pond plants, and a couple of weeks later had hundreds of tadpoles. The pond has been a great success and by late summer I had at least 5 large-ish frogs (green frogs), with many more small frogs hopping around nearby. So far, I've left the pond completely alone and it's done great, becoming a neat little ecosystem with tiny snails and various water bugs in addition to the frogs.

Now it's fall and leaves are starting to clog up the water. Is this ok, or should I remove some of them? I'm also looking for advice on how to overwinter. I'm in Zone 7b, and we usually get a few weeks when the ground freezes about 6-10" deep. I'm anticipating that the water surface will freeze over, but that the rest of the water will stay unfrozen. There's plenty of muck and dead leaves in the bottom, and relatively soft soil around the pond, so the frogs can burrow in to hibernate. Does anyone have experience with overwintering an outdoor frog pond? I'd be delighted to hear what you have to say. Thanks!