What kind of silicone is safe for your aquarium?

Most clear silicone sealant packages will be labeled as safe for use in glass aquariums. Colored or white silicone sealants always contain chemicals that are toxic to fish and other aquarium life; however, not all clear silicone sealants are safe.

Silicone sealants should be evaluated on a case-by-case basis. Even fish-safe silicone sealants with non-toxic mildew inhibitors are not necessarily safe for all aquariums. Silicone sealants are only appropriate for use in glass aquariums, never acrylic, since silicone will eventually peel away from the acrylic aquarium walls due to the oils present in plastics. This leaves the tank vulnerable to leaks.