Dear God, is there anything more boring than waiting for glue and silicone to dry?
I siliconed one of the BGs to a tank yesterday - I used two tubes of silicone, and if I had a third on hand, I would have used it too.
I spread the silicone out so it covered the entire back of the BG like icing on a cake. I laid the tank down on it's back (on bubble wrap - the bubble wrap that came with the light - lol) then put the silicone covered BG in, wiggled it around to get good contact, and pressed down. Some silicone oozed around the edges to cover the side, top & bottom - a good thing.
Then I laid a plush old towel on the BG and put bags of gravel on it for pressure. I left that for 24 hrs. Now I have re-siliconed the edges to the tank - while it was still wet I used a single edge razor blade to scrape off any messy smears.
I cut up some driftwood pieces & Gorilla glued them to a river rock to help hold it down while it becomes waterlogged, and I Gorilla glued the wood pieces to each other, too.
Now I'm waiting, waiting...
While I was waiting, I read up on the use of Gorilla Glue in aquariums. The Gorilla site itself has a question & answer forum, and much of it pertains to tank use. They say that once it cures for a full 7 days, it is completely waterproof and will never leach anything into the tank - fresh OR saltwater.
Good to know!
But now I have to wait seven days! lol