Bubdonna,
That's a funny screen name you have there. Is it a nickname, or how did you come by it? Anyway, welcome to the forum.
First, I don't know the first thing about keeping salamanders alive in captivity, but perhaps somebody here could help you with the basics? You'll be able to convert that eastern garter over to just about any food you want by washing the other food to remove it's scent; then rubbing the clean food against one of those captive salamanders for about 5-10 seconds. It's called "scenting," and it sounds like you'll have quick success with this technique.
Second, the chances of these two interbreeding are extremely remote, and the chances of them producing viable offspring are even less. For some reason this topic has been coming up a bit more frequently lately. Have a look at this post (
garter/water snakes hybrid possiblities?) for more information.
I'm surprised your garter won't take live fish, too. I've never kept a ribbon, so hopefully somebody else will tell you more about their feeding habits. Here's a fun little trick that I like to do to make snakes think they're eating live prey. Just thread some monofilament fishing line (or even sewing thread) through a needle, and stick that through one end of a dead fish. Tie a knot in one end that gives resistance, but can be pulled through the fish after the garter grabs the fish. Put the fish in the water dish for starters and hold on to the other end of the string. When the garter comes to investigate, pull on the string to make the fish move. Snakes go nuts over it, and doing it is a lot of fun. That's why we own snakes, right?
If you want to get more creative, cut mouth-sized chunks of fish from a trout. Wash and scent them with the salamander; then give them some action.
Last pointer for now... be sure to check out the care sheets by clicking on the "articles" tab in the top right corner of any page. Be sure to follow up with us on the progress of your scenting and feeding progress, okay?
Rick