Bill,
Soda-Lime glass has a slightly greenish tint that is only visible when looking through a whole lot of it (like from an edge).
The effect of 1/4" or even 3/8" of it is so slight you would have real trouble detecting a color difference in two side-by-side tanks using "Water White" and regular window glass. For the actual spectral properties, see:
http://www.valleydesign.com/soda-limepic.htm
If you add back that reflective loss you see at the bottom, it is pretty transparent stuff. "Star Brite," "Water White" and other glasses are spectrally purer, but the differences in blue and red are 5% or less and about 0 in the green.
Acryic has a tiny advantage in being whiter, but the biggie is the better index of refraction match to water and lower index reduce its reflective losses and reduced glare from the room reflections.
You can spend a great deal of money on the more transparent glass without getting any useful visual improvement. Trust me. I used to do optics for a living. 
BTW, all we had was the stainless frame tanks when I got into the hobby, and I learned to hate them. :wink: Every one I had used cheap float window glass and was green at all edges. Just harder to see under all that tar. I broke enough and repaired them to know.
Wright
01 760 872-3995
805 Valley West Circle
Bishop, CA 93514 USA
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