I would not go less than 1.5" and preferably 2"
Cheers

Gordon

"George" wrote in message
...

"Paul" wrote in message
. ..
I have a 1200gph mag drive pump. My pond will be approx 1100gals, is this
enough pump? what size tubing i should use.

It should be enough. I would make the tubing at least one inch in
diameter to maximize the flow and reduce backpressure.

George