Jon, I used silicone II (windows and doors). To be honest I am not sure of the difference. Like hopestar said, people have used both.
Toby, it is a standard 30 gal, 36" L, 12.5 W, 17" H.
The inflow/skimmer section is 11", baffels 4.5", Fuge 12.5", and the return section ( with PVC shelf for carbon bag ) is 7".