I have always used some silicone on mine. Not on the gasket side though. I put some on the threaded side, which is the outside in my case usually. This gives me an extra seal on that side. I usually then put a bead around the outside of the gasket/bulkhead, after its been tightened. I have only ever hand tightened.
Agreed its a pain when one needs removing, but on a tank whens that?? Your sump is perhaps a different story though, but I would still do it the same if it was mine.
Never have had a leak that way in 25 yrs. So far.
