What about this stuff? A LFS sells it and says it's totally safe.

http://i134.photobucket.com/albums/q...2/silicone.jpg

ooh.

that's the hard to get stuff. It's good. REAL good. That's what's recommended for doing aquarium stuff in all I've read

Yup. GE SCS1200 is the same stuff they use to build aquariums. You can even adhere acrylic baffles to a glass aquarium when you're building a sump with this stuff.

where did you get it?

A place called Pisces Pet Emporium