Hi, not used it or I believe the main ingredient. This is the note I have from a previous experienced poster.
1-chloro-2, 2, 5, 5-tetramethyl-4-imidazolidinone - The active ingredient is a stabilized form of chlorine
That could explain chlorine increase?
Iíve not heard of issues with it (apart from lively discussion on if it works haha). But in new or unstable or tanks with a lot of cleans I find the nitrifying bacteria is less resistant to meds. So as a guess, the ammonia increase might be from some of the bacterial population being killed off and giving a small mini-cycle.