Depends on where your doser is located and how fast it's pumping from it's location.
Where and how far it has to pump will make a HUGE difference!
My unit pumps about 1Ml per second or so.
BUT MEASURE YOUR OUTPUT, your mailage may vary.
So you need to know how much you were dosing by hand before you can figure out how long it would need to stay on.
For my tank it would take about 50-60 secs per day (50-60 Ml per day).
But if you have a nice controller, you could turn it on for 5 seconds every 2 hours, or something.