If the tube doesn't have aquarium safe or aquarium silicone on the label, skip it.
There are a lot of folks willing to gamble on the safety of your tank decorations. The question is - Are you willing to gamble on the safety of your fish, just to save a couple of dollars? If your local fish shop doesn't carry aquarium silicone, you can order it on line and have it in a couple of days.
Depending on the specific rocks, gel type super glue (all of them) is fish safe.
After curing Gorilla glue is safe, too. Full cure time is listed on the package. Personally, I'd give it an extra 24 hours.