NYCichlidForum.com

I will answer your second question first. Silicone keeps the panes of glass together. The top frame of a tank is structural in nature. It prevents the glass from bowing. Most of the bowing would occur in the center of the tank. That is the reason for the center brace.

You could build a frame yourself, but you would have to use a waterproof material to prevent it from warping and bowing. Many European style tanks have strips of glass glued to the top portions of the glass to make a glass frame with a glass center brace. It is much cheaper and easier to just buy a ready made plastic one.

I was told on another forum that the way my tank is made(center brace not connected to frame) that the frame is ultimately for show purposes. Basically stating i could have a rimless tank if i wanted. Or he said i could create a glass brace at each ends without a frame.

On that setup the center glass piece is the important structural part,the rest of the frame is for ease of putting covers,filters and light on the tank.The one piece top frame now made is a far superior product,and modern covers are going to fit.The new frame for that tank has 2 crosspieces eliminating the need for a glass brace.Some tanks can get away with no frame,like a 30g or a 40 breeder.Some cannot,like a 55g,or the 6' 125g