I'm not familiar with fish in your pond but I'd like to guess that they are some kind of predators (bass, perch etc), aren't they?
In such case at first you should create a feeding spot and try to use only vegetables as food - for example, wheat, corn, bread or something similar. Predators usually will avoid it.
After some time you may try using a rod with the same bait as you used for feeding.
The main idea is to avoid all other fish in the pond.
EDIT: you may try to drop some weeds in the pond and stay still for some time. In cases when grass carps aren't overfed they might eat them and you will witness that. This will help you find out their favorite places. By the way, after watching you can try that weed as a bait - I've heard that Japanese guys use various weeds on hook with good success.
The fish above is a Grass Carp. It is not a predator like a bass. It only eats weeds. All types if hungry enough, but that's it.
Just FYI
The main idea is to avoid all other fish in the pond
