Oh I am SOOOO frustrated!!!

[banditpowdercoat]

Originally Posted by mark

Sorry to hear about the crack but trying to understand how.

If the flange and the nut is fully supported by the glass (correct hole size for the bulkhead) and faces are smooth, would think when tightening, the plastic threads would strip before you could get enough compression to shatter the glass.

If there is any irregularities on the bulkehad flange, it can easilly overstress thin glass.

[Marlin65]

One more reason I love tempered glass. All my tanks and sumps are tempered.
Maybe consider going tempered on the next tank it is not that much more, 7x stronger and has flex to it.
They will drill the hole before they temper.
Tempered is like heat treated steel they heat it red hot to align the particles and then cool it rapidly with big fans. Think of it as the difference between mild steel and tool steel.