Two days ago I did a huge water change 65%+ on my 38 gallon. When I was refilling the tank I use a 5 gal full of dechlorinated tap water about 90% full. I just dump it in and fix the rocks after. Well this time I must of dumped it in too fast or something because it all went on top of the poor red tail shark. Within a few minutes one of his eyes was a good distance sticking out of his head. I did some research and it is caused my nitrogen gas same as when you come up to fast from scuba diving. He is all better now but gave me a good scare and learned a good lesson. Just thought Id give you guys a heads up on the risk of pouring in a lot of water fast.