Have you learned anything about cycling yet? If you put your fish in too soon, and too many in too soon, it would definitely create an ammonia spike. My girlfriend and I learned this the hard way. We lost like 6 fish before we were educated about it enough to keep them alive. I saw in another thread that you lost a tiger barb. Not only would the salt content have shocked it, but a high ammonia would have made it much worse. If you haven't yet, maybe you should google "aquarium cycling" or "nitrogen cycle." Good luck
or there could be a dead fish wedged somewhere just rotting. you need to do waterchanges, you should have no ammonia once the tank is fully cycled. like the previous poster stated if you add too many fish too fast you will also have a spike. id waterchange, get a good ammonia test kit (not strips) and retest after checking for dead fish.
hey savior is this a new tank that you just setup or has it been up for a while?? also, what's your filtration? i had similar problem, see my thread here...