Frags - dumb question

[Aquattro]

Keep in mind epoxy is not glue and will not stick to rock. It's designed to be used to wedge a frag into a space and harden in place, physically binding the frag. It won't stick to flat surfaces, so make sure you've got a rough crevice or indentation to mount to.
Also, most (all?) putty you'll find at the hardware store typically has metal shavings in it, not approriate for reef use.