You can go to home depot and get the G.E. Silicone 1. The one that comes in the blue tube with white writing on it. It will be the window and door stuff. You do not want the kitchen and bathroom one that i think comes in the red tube, that one has anti-mold stuff in it. The blue tube is basically the same stuff that they sell in a pet shop but ten times cheaper. it dries non-toxic and can be used for anything, As i have built several tanks for my cichlid (tropical Fish) collection.