Nitrites not going away?
I have a 3.5g tank thats been running for about a month and a half. Ammonia has been consistently zero for a month and nitrates have been hovering around 5 ppm for about that long as well. It's been taking about 2-3 days for nitrites to get to .25 ppm, at which point I do a 75% water change. I know that a water change that large will slow the cycle down, but I'm concerned that there hasn't been any signs of nitrites getting processed faster over the past month.
I've heard people say that tanks under 5 gallons can't truly cycle, is that true? Am I just doomed to 75% water changes every 2 days? I currently have a betta and two nerites in there, which is slightly overstocked, could that be why my BB can't handle the nitrites?