Neon tetra acting strangely?

First Pet Smart is great for these kinds of things, and they test the water. Second buy an A.P.I. fresh water test kit. It checks for ammonia, Ph and Nitrates. If they are high in any category follow the directions. If it is not resolved go to Pet Smart with the test results, and a vile of water to be tested. And last go to online fish chat rooms, they are great for any advice.