Can anyone let me know if its normal for an old 1987 1/2" glass tank with no center brace to bow about a 1/4"? the tank is 72"x 18"x 23" in good condition it hold water fine but im just curious about the bow. I hear mix comment like, older tanks with no center brace bow and then hear they aren't suppose too. anyone own one or know about them let know. thanks. By the way this tank never had a center brace.