This is the one set of videos on YouTube "aquaponics 05 bell siphon troubleshooting ( part 1of2) that really simplified the construction and adjustment of the bell. he does an excellent job if showing and telling how to adjust the bell siphon. (Syphon may be spelled syphon instead of siphon on you tube.
I have several gbs that are feed off a 4000gph pond pump but each has a seperate ball valve to adjust the water flow. I think that is what Keith was referring too. One side is getting more flow then the other.