i wouldn't worry about the second-hand smoke affecting your display, but you should be very careful about washing your hands before putting your hands in the tank, preparing fish food, etc. bob fenner talks about how he used to work for the state spraying nicotine for mosquito control down south in his younger days, and about the huge fish kills that would result from that. it's worth treating it as toxic to your fish and acting accordingly. just use common sense, like if you aerate your RO water, don't smoke around the air pump.