Hey guys I have an issue and I need help fast. I have an 18 inch RTC in an outdoor pond. I live in san jose california and winter temperature ranges from 55 F in the morning-75 degrees highest( outside temp). sometimes the high is 65F. My Pond is very big and I dont know if the RTC can survive winter In the pond. If he cant I'm planning on building an acrylic rectangle tunnel with a 500W heater attached to the roof so he can swim in if its too cold. Do you guys think this will help? The side panels will be 10inch(height) x 25 inch( length) and the roof will be 18 inch ( width) x 25 inch ( length). my pond is big about 4000 gallon pond. I need help!