I have a question about my nitrogen cycle... I have a 20 gallon tank that's been cycling for two weeks. Yesterday, I had zero ammonia and nitrite readings, using then API master test kit. My Nitrates were 20 ppm. Today, however, my ammonia has jumped back up to .25 or .35 ppm and my nitrates are holding steady at 20 ppm. Does anyone have any idea what's going on? Is it possible to have ammonia and nitrates? I'm new to the hobby and any hep would be greatly appreciated!!!