There are a lot of questions being raised about safety of the silicone sealants that you buy at local Home Improvement store as opposed to paying an arm and a leg for LFS
"aquarium-safe" kind. I have created some great rockwork as well as caves for my new aquarium and then something bugged me about the sealant I used - "GE Kitchen and Bath 100% Silicone Sealant." I have done research, read material data sheets (MSDS), called GE Silicones, and finally learned that GE does not recommend any silicone for aquatic use even though their www.gesilicones.com
website recommends their RTV108 for aquariums. The consumer version of RTV108 is apparently called "Window and Door 100% silicone Rubber Sealant." Any mildew-resistant kinds are not safe. It is a shame that I have to redo all the work I have done, but it is better than dying fish. At the same time I have read other people's letters where they have even used Silicone II and were OK. Please share your experiences and thoughts on this matter.