I wouldn't worry at all with 4ppm ammonia. I've always aimed at 5~6ppm ammonia during my fishless cycling. Once I accidentally dosed a little too much, it went off the scale but it was still cycled in the end.I know that high ammonia <4ppm in a fish less cycle can kill bacteria. But if that has happened would I expect to see a change in the Nitrite/Nitrate readings?
Thanks
Jana