scared fish

Question
2 of my fish keep hitting the sides of the tank are they scared? what can i do about it.

Answer
What kind of fish do you have? Which ones are hitting the sides of the tank? Do you have sufficent plant and or rock cover for the fish to hide in? Have you had your water tested? Do you fish hit the sides of the tank at the same time or at different times? I need this information to better help answer your question.