I've used the regular crazy glue gel and the more expensive CorAffix gel. They both work the same. Your problem may have less to do with hardening too quickly and more to do with getting the flat surface of the tile to bond to the irregular surface of the rock. Or, the rock may have algae on it preventing bonding. I suggest 2 approaches. First, get a toothbrush and scrub any algae off the area you want to attach to on the rock. Then, put a good blob of the gel on the tile and hold it against the rock few a few seconds. This fist method is what I use when I want to attach a coral frag directly unto the rock. The next method is what I use for frag discs. For this second method, I use epoxy putty that you can get at any hardware store or more expensively at the LFS. I knead a thumb sized worth of putty as directed, put crazy glue gel on the frag disc, and stick the balled up epoxy putty on the disc. I then put crazy glue on the other side of the putty that's now on the disc, and stick that unto the cleaned rock surface. The putty with the surface of crazy glue will conform to the irregular surface of the rock. Crazy glue will bond the putty to the disc, and the other side of the putty also with crazy glue will bond to the rock. Works for me all the time. HTH!!!