not the actual return line tubing, but the pvc fitting/spraybar that's in the tank.
Drill a small 1/4" diameter hole in it, just under the normal water level in the tank. Water does shoot out of it, but that just ripples the surface better.
Then when the power fails or you shut down the return pump, as soon as the water level drops down an 1/8" or less, the returnline breaks siphon ( as the air rushes into this hole ).
Works like a charm - very common practice.