Problems with 1 yr old tank

[trevscout]

My tank has been running with nitrate n02 at 0 for a year now and today I checked it and its 0.50 what would cause this? My filter broke today and I replaced it,what can I do to get the nitrates n02 back to 0..Thanks

 

[lion_crazz]

Well NO2 is nitrITES, but that doesn't matter. I understood what you meant by the measurment (.5). Do you have any live rock? Did you have biological filtration in the filter that broke? If you had biological filtration in the filter, it sounds like that when you took out the filter that broke, you removed some bacteria as well.