all you got to do for the silicone is make sure it says 100% and that it has no anti-fungal in it. its better to have the starboard on the bottom because if by any chance you or a fish knock anything down, it won't go straight to the bottom glass, it's safer that way. starboard won't leach anything into the aquarium. we use it to make doors and edges on boats and its a great product. the only problem we have with it is that of the silicone not having a strong bond since it peals easily from it, that's why i said epoxy. if anything sand down the areas were the silicone or epoxy will contact with it.