I have used frozen thawed tilapia for fish, axolotls, frogs, tegus, turtles, etc. without an issue. As with any food it is not exclusive and intermixed with worms/pellets/etc. The only thing I have noticed with some axolotls is it sometimes takes them a bit to get used to/find since it's not a real "smelly" fish, but once they realize what it is they hoover it right up. You could use tongs to feed until they get used to it vs plunking a few chunks/strips in the tank and waiting for them to stumble upon it and, with any food, anything not eaten should be removed from the tank to keep from fouling the water.