Mine are mostly fed earthworms, and occasionally blood worm.
I am keeping mine aquatic. When I start to see signs of them morphing, I drop the water level to about an inch or so, add lots of floating plants and a rock or two to break the surface. So far they are quite happy to stay aquatic. Once I am happy that all is well, and that they are feeding I gradually raise the water level, making sure they have plenty of plants to lurk in. The ones that are staying with me will go into a Walstad style tank.