More on bell siphons...

I recently added a new 4'x8' media based bed to my setup and am running it off of the original tank I created from the IBC tote. Because it has a larger area for the water to trickle through I want to have a good ebb and flow cycle in order to keep dead spots from happening. With an ebb and flow system, not only do you suck air down into the media each time the water goes down, you also ensure that the entire bed gets a nice dose of fresh water with each cycle as well.

One of the inherent problems with bell siphons in larger beds is that due to the bigger surface area the water level tends to drop relatively slowly as the water siphons out. This means that when you hit the bottom of the cycle it is difficult to get the siphon to break so the bed can fill again. I did a bit of net surfin' and found a guy out there with an absolutely brilliant solution to this problem.

Basically he solved the problem by adding a small auxiliary tube to the bell siphon. NOTE: the top of this tube needs to be *below* the height of the internal stand pipe. The bottom end of this tube is cut just above the "teeth" of the bell at the point where you want the siphon to stop (your lowest water level). The tube is placed inside a small cup (A 2" PVC end cap works well). When the water level falls to the bottom of the tube it will also be below the edges of the cup. The water inside the cup quickly gets slurped up in the siphon, but the cup keeps additional water from pouring in. This leaves a nice protected air pocket that will easily break the siphon so the cycle can start over again.

Here's a link to a YouTube video that has some excellent illustrations showing how this works.