How far was it bowing in the middle and how thick is the glass (tank and brace)? Do you know if the tank sat empty for an extended amount of time? Also, wouldn't happen to know what brand it is?
Long come short, you'll have to take down the tank and silicone in the brace again (I assume it's the silicone that failed not the glass it's self?). Depending on the thickness of the tank glass it might be worth buying a new, wider brace from a glass shop. If it sat empty for a long time it might even be worth being pro-active and resealing it.
Chris