About a year ago I had 2 Bala Sharks, about 13 cm long, in my community tank. I have a 200 liter tank and they would swim full force to the other end of the tank and bounce off the glass. Well, unknown to me they had broke the heater glass at the bottom, leaving the coils exposed. When I noticed the heater broken, and before I could unplug everything and stick my hand in the tank to remove the heater, one of the sharks headed right for the heater and was electrocuted! I thought for sure he was a goner. He flapped around for awhile and floated up and down. My husband convinced me to leave him in the tank till morning, and see if he survived. Well, he was alive. He was out of sorts for a few days, but came back to normal. The 2 sharks were so out of control I had to give them to a pet store to get my tank back to normal. My tank was then a lot calmer and the other fish weren't hiding anymore.