With the ammonia reading above 0 tells us that you have a serious water quality problem. As pointed out, the tank is going through some sort of cycle. Most likely something is dead and decaying.
First check your system for any dead fish or corals. The best way to test the corals is smell them. A good coral smells bad. A dead or dying corals will smell extremely foul and bad. Either discard it, or frag it, saving only the good parts, discarding the rest.
Also -
What livestock do you have in the system? (all of it)
What size is the tank?
What kind of filtration, skimming, and circulation are you using?