I bought thicker super glue and a spray for instant hardening
https://www.amazon.ca/gp/product/B07...?ie=UTF8&psc=1
I had some crushed up dry rock powder and some small rubble and tiny rubble. I would glue rock together, throw some rock dust on it and then spray the glue with the instant adhesive, hold for 5-10 seconds and by then it was hard enough.
I wish I had gone back and added some epoxy/reef cement for reinforcement. I had 2 pieces break off moving the rock from the cycling tank to the final tank. It was a lot heavier with it being in the water.