First, welcome to Fish Lore
If you got your fish just yesterday and put them in a new tank, that means your tank is not cycled. If a tank is not cycled, fish will behave unnaturally and they may even get sick and die. If you're not familiar with the
nitrogen cycle, please read about it in the Beginners section on Fish Lore. You should also read the rest of the Beginners' articles.
P.S. A 1.5 gallon tank is too small for Neon Tetras. I'd recommend at least a 10 gallon tank for Neons. Neons also need a heated and filtered tank.