erm.. not sure how your plumbing is, but if the nut on the bulkhead is on the outside of the tank where you can get to it easier, I find using a flathead screwdriver and a hammer to tighten it until the bulkhead is very tight against the glass, creating a much tighter seal. I tried this after noticing some salt creep on my bulkhead, hasn't come back since.
..not too sure if that helps.
