No I haven't had any problems with ammonia spikes. I believe the product I used was called Maracide 2. It was about $15 for one package. I hardly used any of the package. At least I'll be prepared if it happens again or I need to treat my fish for something.
There is a freshwater and saltwater version of Maracide. I almost got the SW because it was cheaper, and then I realized that it was labeled SW. I'm not sure why there is a difference, although the SW version had some additional chemicals in it. I'm not sure if those are FW safe or not.
--- Dave ---