ammonia help

[ILLEGALspoon13]

Hey everyone. First post on here and have a quick question. I set my new tank up about 2 months ago. Let it cycle with live rock and the live sand. After it finished cycling I added a few damsels and watched how they did for a few weeks. Two weeks ago I added a couple corals and they are all doing well. After the cycle the ammonia was at 0 nitrite was 0 and nitrate (after the water change) was a little over 0. I did my second water change a week ago and everything was the same( I check levels about 36 hours after the water change). Now a week later I tested the water again and I have an ammonia spike. It's around .25ppm. What could cause this to happen?

 

[Defect]

Maybe feeding to much and the food is decaying causing ammonia to spike. Im sure there are lots of different answers you will get.