Sequence does an amazing job with their Primer Alpha pump.
CREATE AN IDEAL ENVIRONMENT FOR YOUR KOI WITH THE PRIMER ALPHA PUMP
It combines everything you need all in one device: basket-type pre filter, self-priming capabilities, and fully enclosed motor with fan-cooling.
Most pumps stop pumping water when there is air in the line, but not the Primer Alpha. It has an internal diffuser, which allows for displacement of trapped air and keeps the water flowing. The Primer Alpha helps you raising your koi in ideal pond conditions for nurturing Grand Champion Koi.