Hi LiamB. It seems like somehow, that 8 gallons you took out refreshed everything and removed the nitrites. My best advice is to keep testing for ammonia and nitrites and the next time you get a reading for nitrites, don't change any water until the nitrites reach 2.0ppm or more. Then do a small water change like you did before. The key to successfully cycling fish-in is to stick it out until the ammonia and nitrite reach danger levels. Otherwise, there will not be enough to start the cycle. I've made the same mistake; in my desire to ease my fish's discomfort, I removed way too much water and stopped the cycle cold.