look at Marine Aquariums South Africa calculators
scroll down to the glass thickness calculator
6mm with euro bracing will work, but 8mm would be better
This is slightly shorter but wider than a standard Daro 90L tank. Those that almost all pet shops do sell. And they are 6mm. So could be done. Bottom pane should be double if you use 6mm.500L x 390W x 390H
Euro bracing is a glass strip, at least 100mm wide that runs all around the top of the tank. It allows you to use thinner glass on the sides compared to tank without bracing. Basically it prevents the long sides from bowing out.
But with your tank of 390W, it will not work.
This is slightly shorter but wider than a standard Daro 90L tank. Those that almost all pet shops do sell. And they are 6mm. So could be done. Bottom pane should be double if you use 6mm.
Did you try the calculator
As far as I know the calculator defaults to non euro braced tanks.he calculator says 3mm for the sides and 5.9mm for the bottom hope im using it correctly.