Aqueon Silicone Aquarium Sealant, Black, 3-Ounce (3 Pack) Pack of Three 3oz Aqueon Silicone Aquarium Sealant, Black Our 100% silicone aquarium sealant is easy to apply and waterproof to stop leaks. The high strength silicone creates a permanent seal that will not crack Or shrink and is non-toxic making it perfect for use on all aquariums. For standard aquariums use clear and Black Seal aquariums use Black sealant.