There have been cases of larvae raised on pellet mash, but it's not very likely to succeed. If it has external gills, it's definately a salamander/newt larva, not a tadpole. I don't know where you are in VA, but there are plenty of native sals there, and also red spotted newts in some areas. If you tell me what metropolitan area you live in, I might be able to help you find a source of live blackworms, as I used to live in VA. Another alternative is to use pond water, which has lots of little micro-organisms in it.