The GE, 100% pure silicon in the home improvement centers are much cheaper than that marketed for aquariums. GE has two lines, I forget the full name, but thy'r labeled ... I or ... II. The original one (I) is labeled as aquarium safe, but I don't believe (II) specifies aquariums. The important thing is that they have no anti fungus additives, latex etc. which many caulks do.
Or on the other hand, a plain 29 with black edging is only about $35 brand new. Might not be worth the hassle if you ask me.