Originally Posted by
MadMax
I can tell from your picture that the gasket is shot, either from over tightening, misalignment of plumbing, or improper gasket to start with.
You don't have to drain the entire tank, only enough water to clear the upper teeth of your overflow, then drain the box (only) and replace the bulkheads. I say bulkhead(s) as in plural because it makes sense to replace both while you are at it for preventative reasons. A) bulkheads are cheap, B) you've got the overflow drained, and C) provides you the opportunity to improve your plumbing. For instance, I would replace everything AFTER the bulkhead with FlexPVC instead of rigid pipe for this very reason. Flexible pipe allows for movement in the lower structure without transferring undo stress upon the bulkhead fitting. You were lucky this time.....the next time you may very well crack the bottom of your aquarium which mean full aquarium replacement, do not stop at go, do not collect $200.
Do not simply fix; improve