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.