well i have a pond at my house. when we go fishing in it they tend to go for the worms more then anything else. If that doesn't help i would visit a local pet store or google it online.
I would also put some water in the area your keeping it in. You know those fish tanks where they keep those painted tertals in when you go to the pet store? If you know what I'm talking about try something like that but not as pig and not as costly!