Super glue, super glue gel --- theres a two part epoxy (make sure it says aquarium safe if you don't get a fish brand name).
For your superglue make sure the ingredient is cyanaocrylate.
Do not use stuff like gorilla glue, etc.
I picked up super glue gel at Lowes for like 1.87 -- and I've heard other places have aquarium safe two part epoxy but I have the two little fishies brand or something.