Ok, in reference to the tank I worked on last night:
He got into the office this morning and there was water around the sump and on the floor - not much, but any water is a bad thing when it's not in the tank or the sump!!
I wasn't there, but he figured out that the return pump hose connection at the bulkhead appeared to be the source. I happened to leave 10 feet of 3/4 ID hose there (how about that!) so he replaced the return hose, but it's still leaking. He said that the nut on the fitting was a little loose, he tightened it, and the leak slowed, but still slowly dripping.
My guess is that if the bulkhead was at all loose, all the work we did on the sump (total removal and scrub-a-dub-dub) was enough to loosen an already loose fitting, and that means there is probably some sand or dirt that worked it's way under the gasket. I plan on removing the bulkhead and cleaning it up and re-seating it, and lubing it with some plumbers silicone grease.
However, if it's cracked or damaged, I do have the bulkhead from a glass 92 corner bow that I can use to replace it. His tank is acrylic. Will this bulkhead work for his tank? Is the silicone grease OK for acrylic?