The Biowheel is just another (efficient) form of biological filtration. Its function is to provide an oxygen rich home for the bacteria that convert ammonia to nitrite and nitrite to nitrate. It shouldn't have any negative impact on your water chemistry compared to what you are using now. Hopefully things will even improve (lower ammonia and nitrite, higher dissolved oxygen). Just make sure to leave your old filter running while the Biowheel gets a good bacterial colony going (maybe two weeks or more... but I'm not sure exactly).
btw, I'm new to the Biowheel myself... I've just read up on the theory a little