Help my poor neon tetra is hiding and not eating!?

I think that doing the water change that often is stressful to the fish. It is a good idea to use aquarium salt. Just a bit. Most fish like the brackish water. This reduces stress, and helps with the maintaining of a good water balance. I do a 25% change once a month and add water as it evaporates. Doing it daily is more harmful than good. For a tank this size, I would use half of the pint sized container of salt.