Hi, I'm assembling an aquaponics system using half-barrels and Affnan-style mini bell siphons (3/4" to 1-1/4" pipe).  I have read that each grow bed should cycle every 20 minutes, but my question is how fast should it drain when the autosiphon activates?  Phrased another way, what fraction of the 20 minute period is spent filling, and what fraction is spent draining? Thanks for your help on this!