Last night I forgot to close the window in the fish room, and the temp dropped to 40 overnight! The wind was blowing directly into the room when I got up. My 55 and 20 gallon tanks and my hospital Tupperware (where I'm treating a weak Platy) were all down to 70! I about freaked out. Closed the window, turned on the space heater and shut the door. It took hours to get the tanks back up to 79. I did a partial water change on the Tupperware hospital and the water I added was slightly warmer. I was afraid of shocking the Platy with water that was TOO warm. My question is, if this ever happens again, how fast can I warm the water back up without harming the fish? And will they have any lasting effects from getting that cold? Thanks! I'm worried about them after that traumatic experience, poor things!