Perfecto's 100 percent clear silicone rubber sealant repairs leaky aquariums, broken ornaments, and can be used to build small aquariums. Stays flexible, will not crack or shrink, waterproof, harmless to fresh and saltwater fish.
Adheres to: Glass, ceramic, porcelain, non-oily wood, metal, painted surfaces, canvas, fiberglass, some plastics and rubbers.
Instructions for use:
1. Remove old sealant with a single edge razor blade. 2. Empty and clean the tank with isopropyl alcohol. Dry surfaces. 3. Puncture end of nozzle at 45 deg. angle. Apply sealant at a 45 deg. angle evenly to both surfaces. 4. Spread sealant immediately. Remove excess with dry paper towel. 5. Do not disturb peices for 24 hours. Do not fill with water for 48 hrs. 6. Excess can be trimmed after 24 hours.
This stuff works like a charm. Like the other reviewer mentioned, it is going to work best if you remove all of the original silicone. New silicone will stick better to glass than to old silicone. What I would do is carefully use a razor blade and get a good angle and it should cut it right out. Then add the new silicone, nice and neat on the sides and I just slather it on thick and globby on the bottom. Once you're gravel is in, you won't see it anyway.
In ANY resealing project, prep-work is key. Get the old out "completely", clean, clean, clean, and let it fully dry. This product works like a champ and dries more clear than ANY other product I've used, EVER!!! Do yourself a favor and buy it in the "caulk tube", you'll acheive a more uniform bead than using the toothpaste tube. I've been keeping fish for over 30 years, and have resealed more than a few times.