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kay, you don't say if this is a surface wave exhibit or a more abstract
version.

my experience with such a large tank was the abstract version.  it was about
12 feet long by 6" wide by 3 feet high.  we used  silicone oil and water.
the silicone oil was clear and colorless, so it was the change in refraction
at that interface that made the wave motion highly visible.

our biggest nightmare was maintenance (imagine that)  problem was there was
only small access ports at either end.  when crud formed, it was near
impossible to clean.  we solved the problem by  pumping liquids out, tying
towels to rope and treating like giant pipe cleaner. flush with water &
repeat.  this was a full day's work for two people.

also, it sounds as if you're going to have the visitors push/pull
'something' to create the wave motion.  if so, keep in mind that there is
going to be a large resistance to the movement of your paddle.  ours was
initially geared, but at the expense of frequency.  (geared so a kid could
drive the paddle meant you couldn't then crank fast enough to really affect
freq.)

more info on my experience? call me or e-mail. happy to share.

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