I have a 40 gallon critter tank (breeder 36x18x17 with 6mm glass thickness) that I was thinking of using as an aquarium. I've heard that they shouldn't usually be filled more than half way with water as they may leak or bust. I had three turtles in it for about 2 years with the water level about 3 inches from the top and nothing happened. Will I be better off just getting another tank??