Aquatic mosses such as Java moss (Taxiphyllum barbieri) are some of the easiest aquarium plants to grow and care for. It is also one of the most readily available. Almost anyone with a growing clumps of moss will have extras for sale or trade with other fish keepers. Planting it is easy too. The trick is to keep it stationary long enough to attach itself to something. It can also grow free floating.
Wet the surface of the wood so that the moss will not dry out and will stick to it easier when working.
Lay the moss flat across the wood. It is okay if the moss does not cover all of the wood and there are some gaps. Try to get as much of the moss in contact with the wood as possible.
Tie the cotton thread around one end of the wood. Be sure to leave extra thread on the end of the knot for later.
Slowly wrap the thread tightly around the wood holding the moss securely against it. It does not have to be perfect. As long as the moss does not fall off it is fine.
Continue wrapping the thread around the wood until all the moss is held down, then tie it off using the extra thread on the first knot. If you can shake the wood and the moss stays in place it will be okay.
Place the wood and moss in your aquarium or pond. The cotton thread will naturally dissolve after a few weeks and the moss should attach itself and grow along the wood.