(R)UGF plumbing

The submissions on lighting have been really good and helped me understand the
issues a lot better.  I was wondering if anybody had seen a study of aquatic
plants grown under identical conditions with different lighting?  Can we tell
how much better plants would grow if they had a wide spectrum?  Keith is saying
this whole issue is not as important as we suspected and I would like to believe
that is true.  It seems like a hot topic for university research!  :-)

I'm planning to set up a RUGF system with a vermiculite/soil/gravel substrate
this week.  I'd like to include a removeable PVC tube which I can connect to an
existing UGF system which I could use for the iron/peat leaching experiment.
The problem is the existing lift tubes are too short, too narrow and not
removeable.  Any suggestions for plumbing fixtures?  Is there a threaded clear
PVC coupling or some type of swaged coupling?

           |   |<- PVC tube (replaces old lift tube)
           |   |
           |   |
           [===]<- coupling device??
           |   |
***********|   |*****************
***********|   |***Substrate*****
=================================<- existing UGF

 - Steve