Jeff, I think a big sock would work on the outlet side. A fairly coarse steel strainer would work on the inlet side, and would not collapse. It would prevent your sock from clogging up too fast.

I'm thinking something big, like a large laundry bag would make a great filter.

I don't see any reason to sterilize the water. Anything small enough to pass through a fabric filter would be carried into your pond by birds and turtles anyway.

Shrimp