It is now 3 weeks since I have put my fish in the tank. I have 3 black skirt tetras in a 20g tank with a whisper power filter. I am doing a fishy cycle. I have done 2 water changes, the first was after the first week. That was a 25% water change. The second was today. I did about a 20% water change. My ammonia is at .25 or .50, unchanged after this second water change. I have a hard time distinguishing between .25 and .50. My nitrites and nitrates are and have been at 0. I have an API master test kit. I have not touched anything within the filter during this time. I should be reading something for nitrites. Any help would be greatly appreciated.