I have no life, just fish
I had read about doing this a couple years ago and just got fed up enough to try it. What you do is drill a hole in the top of the overflow siphon tube and glue a short piece of plastic tubing to it. Then attach a hose from that to the venturi intake on one of your power heads. This will pull out any air bubbles that collect in the siphon tube. It has been working very well. It does not have enough suction to restart a completely empty tube. You have to manually suck the air out of the tube to start the siphon, but once that is done the hose to the venture keeps any air from collecting.