I also have 5 Spotted Salamander larvae. I found their eggs in a pond while searching for frog eggs. When they formed into what were definitely not tadpoles I looked for common salamanders in my area and identified the eggs. Only 7 hatched because the other eggs went bad and I didn't realize it at the time. 2 of those 7 died.
They are 2 weeks old now and eating live brine shrimp (which is why I have the little shrimpies in the first place). I have my favorite in it's own container because I'm going to keep it if it lives, 3 in a larger container, and one in quarantine because he keeps laying on his back but isn't dead. He ate today so I'm not sure what's going on with him.
They started off in pond water, then pond water mixed with treated tap water, and now just tap water because getting to the pond it tough and ends up with me covered in ticks. They're big enough not to rely on the micro organisms anymore so I'm pretty sure it's ok.