So here's an update:
I got an impeller/cover and installed it, it seemed to be working great for a few days.
We had a pretty bad electrical storm a couple of nights last week. I woke up one morning to find that all of the fish tank pumps, including my two AC20 filters on my FW
tank, had all failed. I went and bought a new Mag 12, installed it, and we were working fine once again. Less than 24 hours later, my brand new Mag 12 wasn't working (no power hits). I put in my backup pump, which is a crappy 600 gph
"Quietone" and it's been working fine for several days.
What is wrong here? Is there something about my setup that makes it so that Mag 12 pumps all of a sudden won't run? My old Mag 12 worked just fine for a year, and I haven't changed anything other than the pumps in a few months.