HELLO EVERYONE!! CEDAR or PINE Driftwood...both are very aromatic....find a place on your driftwood...preferrably on the bottom and cut it or gouge it and smell. Pine is usually very light in weight and light color if aged...Cedar is reddish if you scratch below the aged part...but smell it too...red oak is of course red from the tannins.
Maybe as a general rule and you are not sure...if it is pleasingly aromatic..dont use it. If not pleaseingly aromatic (stinks) dont use it!!
Tannins will not hurt your tank or fish....will NOT crash your
pH, it leaches out slowly....and regular water changes will clear your tank as the tannins leach out.