We put tilapia in our pond in 2009 to eat the duckweed. Here's Sarah with a
nice string of them.
We've also stocked the pond with catfish and bream.
The pond snakes like tilapia, too!  We have both poisonous and non-poisonous
water snakes.... and, yes, we often go on evening "snake hunts" to thin the snaky
population.   We don't stock the pond to feed snakes!
Tilapia are good because even though they're a non-native species, they
cannot survive a winter in our area, so they cannot threaten native fish.  
They eat the duckweed, reproduce like rabbits, and grow into a nice sized
It's not uncommon to find a mother turtle digging a nest for her eggs.  They
eat the fish, too, but  I don't have the same animosity for them that I have
for the snakes.
One of the more unusual animals from the pond: a leech.
(That Sarah had to keep for a few days in an aquarium.)
We're so blessed to live on a farm surrounded by nature....until I find a baby
snake that the cats have brought into the house!

On the positive, everyday for Sarah is a science lesson of some kind.
This 5 lb. catfish appeared to have been bitten by a
snake, so we caught it to photograph.   (2014)