Center Brace Question

[lemon604]

I bought this 2nd hand aquarium. It is 120 gallon 60x18x24. The glass is very thick and it didn't have a center brace. The previous owner told me it did not came with it because of the thickness of the glass. If I want to put a center brace, where can I buy the top trim with center brace? If I leave it as it is, how safe is it? I'm worried about bowing. I saw online that I can put a glass in the middle and use silicone to hold it together (does that work)?