Originally Posted by tadpole
The size of the piping was not given in the opening post, nor was the type of rock or width.
For a 24" high bubbler, I would use 1/2" piping. You are not trying to create a waterfall or a geyser, but, at 24" height, a subtle feature with some ambient background noise IMO. If building a larger feature that is intended to be the focal point in the landscape, everything is increased proportionately.
Aquascape recommends, for example, 3/4" piping with an 800 gph pump on all of their single basalt columns up to 3' height and 3/4" piping and a 2000 gph pump on their sets of three basalt columns or about 667 gph per column. With 1/2" piping you can get the same effect with a 300 gph pump using less water and electricity.
It's really a question of what is the final effect that you are trying to achieve and how much impact you want the feature to make.
Got ya. Thanks for the reply.