Hi, I've had my 10 gallon tank for about 3 months now, cycled for about 10 days (fishless cycle) then I took a sample to my local fish store and they told me it's good to go... so I added 2 platties. About a month later, and after the bloom disappeared completely, and things seemed to be stable, I added 3 neons and 2 guppies (over the course of 1 week). I ordered an API test kit in order to monitor my water quality, and it arrived today. To my surprise, it seems like my tank never cycled. I have nitrates and nitrites at 0 ppm, while my ammonia seems to be around 4.0 ppm. I freaked out and did a 50% water change, added conditioner to the water, and started searching for ways to deal with this. I use tap water, which I just tested it, the tap water seems to have 4ppm ammonia as well. I don't have any plants in my tank (I didn't want plants right now), but my water is crystal clear. my filter is the standard filter that came with the tank and runs on carbon and a small sponge, but I just bought an Aquaclear filter and some ceramic media, but I'm worried that my water quality will get even worse if I attempt to change anything now. The fish seem ok, they eat and swim regularly, in fact, if it wasn't for the test, I never would've suspected anything... Any advice is much appreciated.