By Simon Morgan.
Typical “Bogwood” from Aquatic retailers is quite expensive yet it’s perfectly safe to collect wood from nature and use it in an aquarium. Just make sure you identify the tree properly and prepare the wood properly. This site may be a help.
Tank with alder
Tank with oak
Remember to collect wood from rural areas and make sure you have permission. Look for dry pieces with no mould, rot or fungus. It’s also fine to take “cuttings” from living trees but again, make sure you have permission or make friends with a Tree Surgeon.
I prefer to dry out newly cut or collected wood for a couple of weeks to remove any remaining sap, then soak it. Soaking isn’t always necessary but helps the wood to sink and the bark to peel off more easily. Removing the bark is optional.
The best time to collect wood is late summer. Go to a deciduous forest and look for beech and oak. At this time of year the larger trees actually drop branches to protect themselves from dehydration. These branches are usually dry and have dropped recently so haven't started to rot. You can also find fresh wood following a storm.
Drift wood from a beach, for example, is not going to have pathogens that can infect freshwater fish. However, chances are it's been floating around the ocean for months or even several years. It's not going to sink any time soon, so I suggest it's not a good place to find wood. If you do find a piece you like and would like to try it, I suggest soaking it, fully immersed, in freshwater for about a month. If it sinks after that, it is probably OK to use, but there is some unknown risk to bear in mind, especially if you can’t identify it.