My garters NEVER have been willing to eat fish. In fact, several times I've had fish survive for MONTHS in the swimming pool in a tank where several garter snakes resided.
I have had the best luck with earthworms. I go to the woods and dig up very small earthworms (and they are clearly earthworms, NOT red wigglers) from under rotten logs, etc, to feed baby snakes. I find you often have to cut even a small earthworm in half (across it so you have two short pieces, not one long worm) because they will stretch themselves out as far as possible to try to intimidate baby garters into being afraid to eat them. I find garters are usually afraid to eat anything much bigger than their own heads. (Toads will blow themselves up with air to try to get a garter to spit them out when a garter is trying to eat a toad too!)
I managed to get some garters onto f/t pinky parts by first rolling the pinkies in the dirt of the earthworm box & rubbing them on the live worms so the pinkies smelled like earthworm. After I managed to get two adult garters started eating f/t pinkies this way, I offered them unscented LIVE newborn mouse pinkies one day and found out that they snapped them right up, excited by the movement.
I have had problems sometimes getting newborn garters to eat ANYTHING. I've lost a few simply because they wouldn't eat anything at all no matter what I tried (while the majority of babies ate eagerly and quickly learned that when they get picked up, they will be set down in their own private Rubbermaid dining room!)
