Your water will probably start to go brown. This is usual and will not harm your fish. The Bogwood itself will act as a pH buffer. If you do not want this colouration which can last for years, boil and rinse your wood over and over to open any cracks and get the tannin out.
for many acid-loving fish (ie tetras, barbs, danios, loaches, corys, new world cichlids, etc.) the pH drop caused by driftwood can be not only acceptable, but desirable.
