Thanks for the suggestions... I did another version of the fish-tank theme with a larger gutter for where the brochure would be folded.
I disabled hyphenation and indeed, it actually works quite good. I decreased the size of the copy text a little bit while keeping the same leading so that the slightly larger word spaces don't become vertical rivers (11/18 -> 10.5/18). I also allowed for 95%-105% glyph scaling for justification. (I'm using InDesign CS3)
front:
http://www.uninspected.com/files/fish.jpg
back:
http://www.uninspected.com/files/fish2.jpg
The body type is Vectora, the headings are Perpetua because that is what was used for the logo which was already existing. I had also considered Syntax and GillSans for the body type because they are a tad more organic but I settled for Vectora's better readability - and because it's Adrian Frutiger's birthday this Saturday ;)