Silicone

[MikeP]

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

[andsoitgoes]

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

[fkshiu]

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.

[fishmaster]

where did you get it?

[MikeP]

A place called Pisces Pet Emporium