you are correct. it would be fairly difficult to tell. I did tighten it down with the wrench, but I don't think I overtightened it. when you're sittin on your keister and trying to tighten something at arms length, and chin level, but with stuff in your way, looking through two pieces of very thick glass, and just using the little double ended bulkhead wrench, it's kinda tough to get them tight in the first place!
If the bulkhead is what is leaking, I should be able to tell because the threads would be wet. I don't think that's the case, although I can't say I tested them. It appears as though the water is coming from the bulkhead/pvc joint.
MitchelWB