Return plumbing - How to stop siphoning

[How do you stop return siphoning incase there is a power failure again. I am using a spray bar. CAn someone send me pics on how to stop this or discribe it for me.]
 
[Drill a couple holes at or right below water level on the return hose. When the tank drains to the hole it will suck air and stop the back siphon.]
 
[Then the holes aren't large enough, or they are clogged.]
 
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