I just inherited a pond and have a couple of questions

First there is no fish in the pond, it's a liner, 15 foot stream, 18
- 20 in deep, and its about 400 - 500gals

I live in 7B zone.

The pond has a lot of hair algae and am wondering if I can just
Scube it off the rocks.
After the removal of the algae I want to drain the pond completely and
leave it empty over the winter. Is that ok and if yes should I do
anything to the liner?

I figure that I'll revitalize the pond in April.

BTW: There are rocks at the bottom of the pond. Should I leave the,
in when the pond is empty
or take them out?

Kurt