If you live in Amarillo, TX aquarium pharmecudicals are about the only test kit you can get without special ordering, so I, along with a number of other hobbyists here, own one. My test kit registers .25ppm on the ammonia, and since my LFS uses the same kit I can't get an accurate reading. I sent a water sample to my friend in Lewisville and he took it to a LFS there, it came out 0 and he said they used a Salifert test kit.
I would probably think that it is your test kit, but I agree that your tank was stocked entirely to fast.
I would still do a water change, and take a test sample to the LFS.