The small hole thing works, but if you want a fail-safe way of doing it where you don't have to worry about snails, algae or whatever covering the little holes then do the following.
Angle your return pipes up near the surface so when the water starts to back flow once the return pipe opening is exposed to air it will break the back flow siphon. You will have to play with it a little bit to see how high up towards the surface they need to me. If you can't get them high enough, then buy some locline and use that.
180-gallon acrylic mainly SPS, SWC 1A Cone Skimmer, APEX Neptune Controller, 3x MP40w Vortechs, Tunze 6045, Radiums 250w in Lumenarc Minis, Galaxy Ballast, BRS Dosers