Use the "advanced search" function and search for silicone in this forum. It comes up weekly and there are some very elaborate threads that cover it in depth. In short, Momentive RTV103 or 108 gets reccomended the most.
Are you looking to build a tank or something else structural, or some other project where the strength doesn't matter much? If you want to build something structural nothing at the big box stores is good, and most if not all "aquarium silicone"s are not good.
"100% silicone" means nothing.