Seachem Flourish Epoxy
Available in gray or brown
Flourish Epoxy is a malleable clay based on two component resin. This sticky clay makes it possible to stick pieces of hardscape together extremely firmly. Take a desired amount of clay from the tube. Knead this thoroughly (with gloves) so that the material is well mixed and roll it into a ball. Place the ball with Flourish Epoxy on the spot where hardscape meets each other, wait a moment and within 5 minutes a permanent bond will be created.
Use Brown to stick pieces of wood together. Gray is ideal for connecting stones. After 24 hours it is completely hardened. This can be done both above and below water. Completely safe for fish in the aquarium.
It can cause irritation to the skin during processing. So use gloves. Avoid contact with eyes.