Need help connecting another pond to a already existing above the ground pond

[Joseph demir]

How would I connect these together I started to dig out the rough shape of the second pond I wanted to do this because I wanted to see my smaller fish and would look pleasing

 

[j.w]

@Joseph demir

 

[GBBUDD]

Simple really build up the triangle so the walls are at least 6 inches taller than is the desired water level . and that level should create a waterfall back to the pond