I don't think purigen eats ammonia. It isn't zeolite.
Sent from my SGH-M919 using Aquarium Advice mobile app
You are correct. It isn't zeolite.
From Seachem... "Purigen® controls ammonia, nitrites and nitrates by removing nitrogenous organic waste that would otherwise release these harmful compounds. "
Controlling nitrogenous compounds in a cycling tank can AND does warp the cycle and makes it unpredictable at best though. Unpredictable uptake and test readings are not something you want before the tank is established.
JMO/E.