Hi Mark, I don't know that a filter is necessary, not a bad idea though. I've never installed one. The clearances in these pumps are pretty big, they can be measured with a tape or ruler.
The one pump I had stick just had a few rust spots that got be about 1/16" tall and touched the pump impeller. This happened when the pump was not running. These motors have virtually NO torque, so the motor just couldn't start moving. I just scraped the rust spot with a pocket knife, and brushed it with a wire brush and reassembled it.
I don't know how much a filter would slow down the circulation, I have no experience with them. I think since you are pumping fresh water from your water system, it should be free of sediment?
Looking forward to the results of the pump install.