Backyard Aquaponics
A place to discuss aquaponics

If it won't stop flowing then the in-flow is simply too much... you'll have to play with it some more.

Are you sure the "flow" you speak of isn't coming from the hole at the base of the standpipe. There is no need to have a hole at the base of the standpipe, that's for timed flood and drain systems.

Am I reading right that your running the pump on a timer with a bell syphon?

As Charlie is eluding to: you don't need to run a timer and a bell siphon together.

Either remove the bell and run timed flood and drain or remove the timer and keep the bell(s).

If keeping the bell(s) you will need to install ball valves where the water enters your growbed to control the flow.

If it won't stop reduce the flow, if it won't start increase the flow.

Read Mr Damage's post in this thread for directions on how to solve siphons problems (post #8): viewtopic.php?f=8&t=12584

I agree with all above. Affnan principle is great if have low pump flow but creates problems with higher flow rates. Take the funnel off the top of the standpipe or just make a new standpipe and try that.

Just remove the bell siphon and run Constant Flood or run timed without the siphon. Either of these works better than using the timer and the siphon. There isn't anything wrong with using a pump on a timer and a siphon but it is more likely to fail.

Yep, ball valves are handy, adjust the flow a bit and you'll have it working in no time.......

Cant tell from pics do you have enough holes around the bottom of your media gaurd , i have one that i have to turn often as i guess roots restrict flow and give problems . It might be the flow is on the quick side and GB cant drain quickly enough to drop water level low enough to let air in. I have holes like yours and two rows around the bottom as close as possible .