Hi Philly,
A net over the pond, well staked will do the job to get the birds and coons out. Might the one your thinking about be a Osprey?
For above ground, you can buy a stock tank, aka water trough. I have a round one that is 750 gl's I use for a Q-tank, set up with a laguna 1500 pump & fountain head and the laguna bio filter thats expandable.
The nice trick with these are you can do alot with them, like build a gazebo around it, effectly protecting it through winter. Useing rolled insulation on the outside you can also rock up the outside as well, giving it more protection and looks nice!
Stock tanks come in lots of different sizes, from 50 gl's up.