I started a 75 gallon tank a month ago with 4 tetras and 2 zebra danios. I did this based on advice from the pet store. Unfortunately I found this forum later and now know that this is not the best way to do it. I've been testing for ammonia only about once a week and levels have never been above .50 ppm, usually less. The last pwc I did was a week ago. Today I tested ammonia, nitrates and nitrites and all are 0. This is the first time I've tested for nitrites and nitrates so I don't know where I am in the cycle. Can someone give me some advice on where to go from here? Is it possible that the cycle never started or it completed already?