A bell siphon is a clever mechanism that uses water pressure and air displacement to automatically drain a container once it reaches a certain level. It is most often seen in aquaponics systems, where it helps control water cycles between tanks without the need for pumps or electronics. The bell siphon consists of an inner standpipe that determines the maximum water height and an outer bell that traps air, allowing suction to begin when the water reaches the top of the standpipe. When water rise