Ok, I traded a guy some dead saltwater coral for some small power filters and approximately a 40gal tank (36Lx15wx16t). He says he used the tank several times as an aquarium with out any problems and we filled the tank up at his house and no leaks. I know the glass is not tempered because there is a chip in it. My concern is the glass is 3/16 inch thick. I have a 20gal (24x12wx16t) that has the same thickness of glass. Is 3/16 inch thick glass correct for an approximately 40gal aquarium or is this tank for reptiles. I checked on line and found info saying the glass should be thicker, but I know the 20gal is for fish and has the same thickness as the 40 or so gal, so this is my delema. Anybody have some suggestions or input regarding this? 