I recently acquired a used 75 gallon (48x18) tank. The trim / frame is in pretty bad shape, splits or cracks in the plastic at all 4 corners. I would like to replace it.
I called glasscages.com and they said their frames were specific to their brand. I called my lfs and they asked me what brand the tank was because their was a difference in brands and the frame could end up being too big or too small, depending on what I had. They also said they would not order one for me and then be stuck with it if it did not fit. I don't know what brand it is and the person I got it from did not know either. There isn't a label on it.
I heard of people building their own frames out of wood but I haven't found anything showing how to online.
I have also seen where people have replaced individual cross braces with plexi and "L" brackets. But they were replacing the rest of the trim.
In my case the existing cross braces are still holding. but the remainder of the trim is in bad shape.
So I measured the frame for a glass top like freshfins suggested and it shows to be Perfecto/Marineland. I called customer service and they said I couldn't go by those measurements and that if it was a perfecto or marineland tank there would be a label. They also said I would have to get a replacement from a local store that I could not get it direct from them.
I'm going to check tonight again for any kind of lable, but if I can't find one I guess it is back to the drawing board.