Nitrites in an established aquarium?

I've had a 10 gallon freshwater aquarium for about 9 months now with no problem. I just got a test kit and tested the niTRITES (NO2) and got a reading of 0.1ppm. I know this is bad but besides water changes what can I do? Anyone got any tips/advice/websites with good information that they'd like to share? Thanks in advance