Keeping bullfrogs contained...

[Vicious_Fish]

All good advice but I think you'll have to face the fact that unless the pond is completely enclosed you run the risk of the frogs escaping or being killed by predators. You'd be surprised of what kind of animals live in your area. Raccoons, skunks, opossums, foxes and passing herons could all make a meal of your frogs. You could always try a few tadpoles, let them grow up and hopefully they'd stay around and breed.

 

[bettagurl]

All good advice but I think you'll have to face the fact that unless the pond is completely enclosed you run the risk of the frogs escaping or being killed by predators. You'd be surprised of what kind of animals live in your area. Raccoons, skunks, opossums, foxes and passing herons could all make a meal of your frogs. You could always try a few tadpoles, let them grow up and hopefully they'd stay around and breed.

These are my tadpoles - well not anymore, but they were raising in my pond.
I really don't see how anything could get in.
I think I forgot to add that it will have a top of some kind... No raccoons/skunks/herons/opossums/foxes getting in.

Yes, I learned the hard way about herons. We have a huge blue heron who cleaned us out last year, he still sits in our front yard, even though he can't get into the pond.

 

[bettagurl]

I was actually thinking of using the summer as a time to try to do a greenhouse around the pond.
When you DIY it's not that expensive at all.