Cross Member Sprung Up !

[Cheechako]

I would remove and replace it. Taper a board and glass it in. Alternatively, you could just leave it, grind the area well and glass over it creating a glass structural piece. The old piece would then just be the core. Better out of there though. Use no nail or screws under where the tank sits! they slowly work out and rub a hole in the tank. Seen it happen twice.