I dont recall seeing a hose clamp on the tank, but I am not sure I have looked that closely. Is there any type of rubber grommet between the tank and the PVC? If it is just straight PVC, I think I would try to goop it up with a little cement all around the connector and see if I could seal it off. There should be very little pressure on that connection so I would no think it would take much.
The "best" way to deal with it would be to disassemble it all and re-cement it, but that would by a royal pain! Worse case I would wrap it with some sort of rubber hose covering and use a couple of hose clamps to tighten it down.
If you continue to have problems, send a few pics up so we can see exactly what you are dealing with.