If I wanted to do something I could be sure would help protect fish during an ammonia event:
1) lower pH (7.8 is fine in a pinch, I wouldn't try to push the aragonite buffer around ~7.6)
2) add algae
3) add carbon (vinegar or whatever carbon you already use in your system)
4) add aeration (heterotrophs and nitrifiers both need O2 to work well, and the die-off could push O2 low.)
edit: 5) and y'know... water changes
Those are all incontrovertible and do not require trusting any unsupported manufacturer claims