ok i just picked up a 150 gall glass tank and the inner corrners feel almost like they dont have any silicone u can feel its thire but not my other tanks
put it in the garage and fill it with water and let it sit for a week or two. if it leaks, re seal it. i bought my 130 tank used off of craigslist original silcone and the tnak was built in 1997, holds water like its brand new.
i had that problem before on a 120g a while back. just reinforce it with another layer of silicone; that worked for me and never leaked. i believe till this very day the new owner is still using it leak free!