i will be getting a 240 gallon tank next feb. for my common snapping turtle. she will get to between 12 to 16 inches in shell length. maybe 18 but thats rare. i was going to build a pond in the basement for her but now my family is attatched. so weve decided to go with glass and keep her in the living room. the tank will only be 3/4 full at the most with watter. how think does the glass need to be? 72*30*25 are the tank dimensions.