I just wanted to post this here because the internet is tricky with finding specific information. I went to clean the front of the glass of my aquarium with the light on (never again) and my silver dollar freaked out and hit the side of the tank pretty hard, next thing she was alive, but upside for 10 minutes. She has just begun swimming the right way up again..but I have never seen anything like that! It was like she knocked herself out.. from now on I will turn their light off when tampering within the tank as it seems help them remain calm. But wow. Hopefully no long term issue was caused by that freak out she just had.