why is my fish staying at the bottom of the tank?

Question
I just change the water of my 10 g tank and now my sword tail fish only staying at the bottom of the tank. He looks totelly normal! But he doesn't swim at all! WHY!

Answer
Victoria,                                                    If his fins aren't clamped and he looks ok he might be a little stressed from the water change. I hope you used a siphon to clean your tank and didn't do more than a 50% water change. Check your PH. Let me know, Tina