I'm setting up the 4 ft tank however I'm not too sure if the brace being the way it is, is it going to be safe to do so? So my real question is, is it safe to set up this tank or shall I seek another?
Is it solidly connected to both sides? My center brace in my 55G is plastic and salt is just fine. Make sure the tank is level on the stand and supported on all 4 sides. Don’t let any hang over. If you’d feel safer with additional support then you can add another brace under it. I think you’re fine.
You need to replace the cross member or the tank will bulge out sideways and possibly break.
Use a single sided razorblade to slice the silicon holding the cross member onto the support strips (long thin bits at the top). After you have removed the broken glass, cut all the old silicon off the support strips where it was sitting.
Buy a new piece of glass to fit across the tank. Make sure it is the same thickness as the sides of the tank.
Use a piece of wet and dry sandpaper (on a block of wood) to smooth the edges off the new piece of glass.
Wash the new piece of glass with warm soapy water a few times to get rid of any oils on it. Rinse it well then dry it.
Then silicon the new piece into place and leave it to dry for a week.
Then set up the tank.
Oh, wow! I didn’t even notice that. I would reinforce it with another piece of possibly acrylic over it attached with clear silicone. It’ll give it more strength. Edit: Sorry, Colin T replied while I was typing.