I dont understand your reasoning. You siad that in the winter the tank would stay that cold, well what about the other 6 months of the year? I really think you should spend a little more time researching sharks before you get one. I understand the desire to have one, but you want to be able to keep it alive and happy right? Read a few books then decide for your self what kind of shark and what kind of tank you want and need. Then you wont have to hear people give you the answers you dont want to hear. JMO