10mm glass 2.4x600x600 with euro bracing as well as normal bracing, it looks like the centre brace has given way. ( do not know age of tank,not new.)Just as well no one was standing in front of it as the force of water threw the glass across the garage and smashed a 1200x450x450 tank also with guppies, also causing my fluval 404 to pack up. 2 broken lights. I managed to save about 50 and my skunk loach (first time I have seen it in months.) Water travelled as far as the bedroom. Looking on the bright side it could have been worse. No one was hurt and thankfully it was not my Discus or gold nugget tanks.