There is nothing like real wood aquarium driftwood to make any aquarium look more natural and beautiful. In most natural aquatic habitats, fallen trees, roots, logs, and other chunks of wood are all part of the natural environment. Fish and other aquatic life use these woody debris for places to hide and find food, and beneficial bacteria colonize on wood.
Aquarium driftwood is not necessarily the kind of wood you pick on the beach, driftwood is what any wood that is put into an aquarium is called. Some types of wood are better than others for driftwood because of their different qualities and chemical properties. A good wood for an aquarium is wood that looks good, provides habitat, resists decay, and is not chemically toxic.
A common problem with natural aquarium driftwood is wood will release tannins into the water. Although tannins at low levels are not directly toxic to most fish, enough of it can reduce the pH of the water and also color the water. There are some aquarium driftwoods, such as manzanita, that are popular because they release less tannins than others. Manzanita is also a wood that will sink in water after it becomes saturated. The ability to sink without being weighted is another good characteristic of good driftwood for aquariums.
It is highly recommended that you first soak a new piece of aquarium driftwood in water for a while before putting it in your aquarium. Soaking it will leach out much of the tannins and and saturate the wood so it will sink. The water should be changed every day or two and depending on the type and size of wood, it can take a couple weeks to a couple months for the higher levels of tannin to leach out. You should notice over time less color in the water as you continue to change the water.