I have heard that it will help turn my tank water brownish because of the tanning? Is this true.
I presume you cannot just put any wood in from the garden?
as noted, it's probably best to stick to gear from an LFS.
but, yes, it will, most likely, make your water brown to some extent. first, tannins are not bad for your fish. so if you can put up with it, it will go, slowly. you can add an extra filter with carbon, inside. this will clear your tank faster. unfortunatly, even if you boil and soak your log, it will, more likely than not, still give off tannins. its just something you have to deal with. many people boil and soak, as i have mentioned. i, however, do not. i have never suffered from problems, because of that.
ps, oddly i find "Maparni wood, gives off more tanninss, than Bogwood. just stick to a good quality LFS. the problem will go with time.