For those that have a existing pond with no bottom drain installed, the Retro-drain may be what you are looking for. It sits on the floor of the pond with the pipe running along the contour of the ponds bottom. The pipe is then brought up the walls and out of the pond where it ties into the suction line just like the previous bottom drains. It comes with adapters to fit it to 1 1/2", 2", 3" and 4" pipe.
(note that 3 inch Tetra drains, 4 inch drains and 2 inch drains are made out of PVC where as Retro-drains are made of ABS. If cementing ABS to PVC, use specialty cement.)