I have recently started a 5 gallon tank. I have been cycling it using biological additives and I have been doing water changes once a week. For the first two water changes, there was only nitrates present, but for last two water changes, there has only been 0.25ppm of nitrites present. No ammonia or nitrates. I have been monitoring nitrites through the week and they have yet to change. I don't know what is causing this and despite doing water changes. I have cholla wood , duckweed, and moss balls in the aquarium and nothing else. I use an aqueon quietflow 10 as a filter with added bio balls. Any suggestions would be much appreciated!