For the rods on mine, I used threaded rod capped on both ends with acorn nuts. Inbetween was sleeved in a chromed pipe...I think it was some sort of toilet part. It was pretty soft/easy to bend.
As for the tube within a tube, I suppose you can do that, but I don't think it will have the same effect. With the tube filled with water, it distorts the view of whats inside.
Hmm...o.k., maybe that isn't so good.:$
The water for mine was pretty cheap. I went with distilled water to try and keep the algae/mold problem to a minimum. I think it took around 6 gallons of the stuff, at around $1.00 per. Another thing to keep in mind, you'll have to water proof the hugger if you do decide to fill the tank with water, just like in Frank's article.
Here are smoe shots of mine I took last night. It's got some funky stuff growing in/on it, but I think that adds to the effect. In the movie, two of the huggers were dead and looked like it, mold and all.
Light on with flash
Light on, without flash
This has been sitting this way for roughly 3 years so the mold thing was going to be an issue reguardless. If you changed the water out every 6 to 10 months, you'd probably have zero mold.
I'd also like to throw out there that the switches Frank used were bought at Radioshack. I don't know about anyone else, but my local "Shack" stopped carrying just about everything for the DIY person, including their switches. I was fortunate to have several on hand so I could complete mine. In the years following the completion of my tube, I did find a local hardware store that supplies the switches needed. I'd be happy to help pick some up for anyone interested. Just pay for the switches plus shipping.
The circular light Frank used is available at most any hardware store. I picked mine up at Lowe's.