White Quackers on New Pond

I have decided to farm. I am not waiting for retirement. I am not waiting to buy farm land some time in the distant future. I am starting now.

I have dug a big hole at the end of the garden. When I say I, I mean Freddy. But the hole is done and Mandisa's ducks are now swimming in the pond. I would still like to plant the edges....But what I would really like to do is put Tilapia in the dam. I have been reading about Tilapia and it sounds like a really exciting idea.
(edit - 11 May 2014 - The duckpond we built is at our residence in Walmer - its a 1500 sq m plot and it still houses the duck pond, though there are no ducks on it and it is now quite overgrown with some Tilapia under the surface and some duckweed floating on top)