Rocks fell when I tried to clean.

[zalick]

Is the Seachem Reef Glue any good?

This will not work for those heavy rocks. This is just superglue. Good for corals etc but not heavy objects that may have shearing forces.

 

[NeonRabbit221B]

Just use two part epoxy... Put the superglue on the epoxy before you smush it into the rock

 

[NashobaTek]

JB waterweld is another one that I have used both in and out of water.