How to get rid of siphon

[TAHK]

So, I have been using the container under my aquarium for ATO with Tunze Osmolator. It has worked well, however, I decided that I needed the higher capacity container and decided to connect Osmolator to my RO storage unit. It is about 20 feet away. I used the Tunze controlled switched outlet for the small Eheim pump and used the plastic 1/2 in tubing for the line. The line comes up about 4Fr and then dips to about 2 feet the pump located on the floor level so the tip of the line goi g into the sump is above the pump.
I do have significant siphon going on. After the pump turns off the water keeps on running for another 15 min or so.
How would you prevent it from happening?
Any ideas are appreciated
Thank you in advance.

 

[Beau_B]

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