Aquascape question

I was hoping to get some direction on the best way to secure the dry rock for my classroom reef project. I have 50lbs of Marcos rock. I assembled the rock without glue / cement on a template of the aquarium, but would like to shore it up before putting it in the actual tank. I would like to stay away from the PVC / acrylic rod route. Thanks in advance.

A reef safe 2 part epoxy works well. Also marco rocks makes a cement you mix up yourself, takes a bit longer to dry. Super glue gel/frag glue by itself or mixed with one of the above works well also