Things You'll Need
It is important that you heat the sealant just enough to soften it, not to melt it. If it melts, it may burn your skin, so protective gloves are recommended. Melting will also cause the sealant to drip, making it more difficult to remove as opposed to it being in one solid strip.
It is almost impossible to remove aquarium sealant without scratching the glass to some extent, so just be gentle to minimize any potential damage. Nonetheless, be prepared to fix any scratches in the glass with scratch remover, which can be purchased at most hardware stores.
Aquarium sealant is a solid, adhesive rubbery gel composed primarily of silicone. It is extremely strong and used to bond heavy sheets of glass together in most aquariums. Along with strength, it's also known for its durability, for it can handle years of abuse and continue to hold glass together despite corrosion by both fresh and saltwater. However, if the situation calls for it, for example taking apart an aquarium, it can be removed quite easily.
Empty the tank and let dry.
Set the dryer to high heat and use it to warm the sealant to be removed, softening it. Do not heat the sealant until it melts.
Using the razor blade, gently scrape the bulk of the sealant from the glass.
Moisten the rough sponge and use it to scrape off any remaining fragments.