With large cobbles you run more of a chance of leaking in low edges by water bouncing off them and running over the sides. Build your side edges with this in mind on shallow runs.
You still can build a small low type waterfall that looks like a spring popping out of the ground.
You can get a 4200gph Big Frog pump from Anjon for a great price. The nice thing is they last!
St.louis Ponds and Waterfalls
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