Will my tank explode???

[Psyire]

Usually the black trim does provide support, but it depends on how the tank was built.

I would be checking to see if the long panes (front/back) are bowing out at all when it is filled. If you detect no bowing, I wouldn't be worried. Usually glass will bow a little before breaking. Being only 18" tall you are probably safe with 3/8" but how the tank was built will play a role in determining just how safe.